On this lesson students are given the opportunity to become acquainted with another unit of measurement of area, the square decimeter, and learn to translate square decimeters in square centimeters, and also practice performing various tasks on comparing quantities and solving problems on the topic of the lesson.
Read the topic of the lesson: “The unit of area is the square decimeter.” In this lesson we will get acquainted with another unit of area, the square decimeter, and learn how to convert square decimeters into square centimeters and compare values.
Draw a rectangle with sides 5 cm and 3 cm and label its vertices with letters (Fig. 1).
Rice. 1. Illustration for the problem
Let's find the area of the rectangle. To find the area, you need to multiply the length by the width of the rectangle.
Let's write down the solution.
5*3 = 15 (cm 2)
Answer: the area of the rectangle is 15 cm 2.
We calculated the area of this rectangle in square centimeters, but sometimes, depending on the problem being solved, the units of measurement of area may be different: more or less.
The area of a square whose side is 1 dm is the unit of area, square decimeter(Fig. 2) .
Rice. 2. Square decimeter
The words “square decimeter” with numbers are written as follows:
5 dm 2, 17 dm 2
Let's establish the relationship between square decimeter and square centimeter.
Since a square with a side of 1 dm can be divided into 10 strips, each of which is 10 cm 2, then there are ten tens, or one hundred square centimeters in a square decimeter (Fig. 3).
Rice. 3. One hundred square centimeters
Let's remember.
1 dm 2 = 100 cm 2
Express these values in square centimeters.
5 dm 2 = ... cm 2
8 dm 2 = ... cm 2
3 dm 2 = ... cm 2
Let's think like this. We know that there are one hundred square centimeters in one square decimeter, which means that there are five hundred square centimeters in five square decimeters.
Test yourself.
5 dm 2 = 500 cm 2
8 dm 2 = 800 cm 2
3 dm 2 = 300 cm 2
Express these values in square decimeters.
400 cm 2 = ... dm 2
200 cm 2 = ... dm 2
600 cm 2 = ... dm 2
We explain the solution. One hundred square centimeters equals one square decimeter, which means that there are four square decimeters in 400 cm2.
Test yourself.
400 cm 2 = 4 dm 2
200 cm 2 = 2 dm 2
600 cm 2 = 6 dm 2
Follow the steps.
23 cm 2 + 14 cm 2 = ... cm 2
84 dm 2 - 30 dm 2 =… dm 2
8 dm 2 + 42 dm 2 = ... dm 2
36 cm 2 - 6 cm 2 = ... cm 2
Let's look at the first expression.
23 cm 2 + 14 cm 2 = ... cm 2
We add up the numerical values: 23 + 14 = 37 and assign the name: cm 2. We continue to reason in a similar way.
Test yourself.
23 cm 2 + 14 cm 2 = 37 cm 2
84dm 2 - 30 dm 2 = 54 dm 2
8dm 2 + 42 dm 2 = 50 dm 2
36 cm 2 - 6 cm 2 = 30 cm 2
Read and solve the problem.
The height of the rectangular mirror is 10 dm, and the width is 5 dm. What is the area of the mirror (Fig. 4)?
Rice. 4. Illustration for the problem
To find out the area of a rectangle, you need to multiply the length by the width. Let us pay attention to the fact that both quantities are expressed in decimeters, which means that the name of the area will be dm 2.
Let's write down the solution.
5 * 10 = 50 (dm 2)
Answer: mirror area - 50 dm2.
Compare the values.
20 cm 2 ... 1 dm 2
6 cm 2 … 6 dm 2
95 cm 2…9 dm
It is important to remember: in order for quantities to be compared, they must have the same names.
Let's look at the first line.
20 cm 2 ... 1 dm 2
Let's convert square decimeter to square centimeter. Remember that there are one hundred square centimeters in one square decimeter.
20 cm 2 ... 1 dm 2
20 cm 2 … 100 cm 2
20 cm 2< 100 см 2
Let's look at the second line.
6 cm 2 … 6 dm 2
We know that square decimeters are larger than square centimeters, and the numbers for these names are the same, which means we put the sign “<».
6 cm 2< 6 дм 2
Let's look at the third line.
95cm 2…9 dm
Please note that area units are written on the left, and linear units on the right. Such values cannot be compared (Fig. 5).
Rice. 5. Different sizes
Today in the lesson we got acquainted with another unit of area, the square decimeter, we learned how to convert square decimeters into square centimeters and compare values.
This concludes our lesson.
Bibliography
- M.I. Moreau, M.A. Bantova and others. Mathematics: Textbook. 3rd grade: in 2 parts, part 1. - M.: “Enlightenment”, 2012.
- M.I. Moreau, M.A. Bantova and others. Mathematics: Textbook. 3rd grade: in 2 parts, part 2. - M.: “Enlightenment”, 2012.
- M.I. Moro. Mathematics lessons: Methodological recommendations for teachers. 3rd grade. - M.: Education, 2012.
- Regulatory document. Monitoring and evaluation of learning outcomes. - M.: “Enlightenment”, 2011.
- “School of Russia”: Programs for primary school. - M.: “Enlightenment”, 2011.
- S.I. Volkova. Mathematics: Test work. 3rd grade. - M.: Education, 2012.
- V.N. Rudnitskaya. Tests. - M.: “Exam”, 2012.
- Nsportal.ru ().
- Prosv.ru ().
- Do.gendocs.ru ().
Homework
1. The length of the rectangle is 7 dm, the width is 3 dm. What is the area of the rectangle?
2. Express these values in square centimeters.
2 dm 2 = ... cm 2
4 dm 2 = ... cm 2
6 dm 2 = ... cm 2
8 dm 2 = ... cm 2
9 dm 2 = ... cm 2
3. Express these values in square decimeters.
100 cm 2 = ... dm 2
300 cm 2 = ... dm 2
500 cm 2 = ... dm 2
700 cm 2 = ... dm 2
900 cm 2 = ... dm 2
4. Compare the values.
30 cm 2 ... 1 dm 2
7 cm 2 … 7 dm 2
81 cm 2 ...81 dm
5. Create an assignment for your friends on the topic of the lesson.
In this lesson, students are given the opportunity to become familiar with another unit of measurement of area, the square decimeter, learn how to convert square decimeters to square centimeters, and also practice performing various tasks on comparing quantities and solving problems on the topic of the lesson.
Read the topic of the lesson: “The unit of area is the square decimeter.” In this lesson we will get acquainted with another unit of area, the square decimeter, and learn how to convert square decimeters into square centimeters and compare values.
Draw a rectangle with sides 5 cm and 3 cm and label its vertices with letters (Fig. 1).
Rice. 1. Illustration for the problem
Let's find the area of the rectangle. To find the area, you need to multiply the length by the width of the rectangle.
Let's write down the solution.
5*3 = 15 (cm 2)
Answer: the area of the rectangle is 15 cm 2.
We calculated the area of this rectangle in square centimeters, but sometimes, depending on the problem being solved, the units of measurement of area may be different: more or less.
The area of a square whose side is 1 dm is the unit of area, square decimeter(Fig. 2) .
Rice. 2. Square decimeter
The words “square decimeter” with numbers are written as follows:
5 dm 2, 17 dm 2
Let's establish the relationship between square decimeter and square centimeter.
Since a square with a side of 1 dm can be divided into 10 strips, each of which is 10 cm 2, then there are ten tens, or one hundred square centimeters in a square decimeter (Fig. 3).
Rice. 3. One hundred square centimeters
Let's remember.
1 dm 2 = 100 cm 2
Express these values in square centimeters.
5 dm 2 = ... cm 2
8 dm 2 = ... cm 2
3 dm 2 = ... cm 2
Let's think like this. We know that there are one hundred square centimeters in one square decimeter, which means that there are five hundred square centimeters in five square decimeters.
Test yourself.
5 dm 2 = 500 cm 2
8 dm 2 = 800 cm 2
3 dm 2 = 300 cm 2
Express these values in square decimeters.
400 cm 2 = ... dm 2
200 cm 2 = ... dm 2
600 cm 2 = ... dm 2
We explain the solution. One hundred square centimeters equals one square decimeter, which means that there are four square decimeters in 400 cm2.
Test yourself.
400 cm 2 = 4 dm 2
200 cm 2 = 2 dm 2
600 cm 2 = 6 dm 2
Follow the steps.
23 cm 2 + 14 cm 2 = ... cm 2
84 dm 2 - 30 dm 2 =… dm 2
8 dm 2 + 42 dm 2 = ... dm 2
36 cm 2 - 6 cm 2 = ... cm 2
Let's look at the first expression.
23 cm 2 + 14 cm 2 = ... cm 2
We add up the numerical values: 23 + 14 = 37 and assign the name: cm 2. We continue to reason in a similar way.
Test yourself.
23 cm 2 + 14 cm 2 = 37 cm 2
84dm 2 - 30 dm 2 = 54 dm 2
8dm 2 + 42 dm 2 = 50 dm 2
36 cm 2 - 6 cm 2 = 30 cm 2
Read and solve the problem.
The height of the rectangular mirror is 10 dm, and the width is 5 dm. What is the area of the mirror (Fig. 4)?
Rice. 4. Illustration for the problem
To find out the area of a rectangle, you need to multiply the length by the width. Let us pay attention to the fact that both quantities are expressed in decimeters, which means that the name of the area will be dm 2.
Let's write down the solution.
5 * 10 = 50 (dm 2)
Answer: mirror area - 50 dm2.
Compare the values.
20 cm 2 ... 1 dm 2
6 cm 2 … 6 dm 2
95 cm 2…9 dm
It is important to remember: in order for quantities to be compared, they must have the same names.
Let's look at the first line.
20 cm 2 ... 1 dm 2
Let's convert square decimeter to square centimeter. Remember that there are one hundred square centimeters in one square decimeter.
20 cm 2 ... 1 dm 2
20 cm 2 … 100 cm 2
20 cm 2< 100 см 2
Let's look at the second line.
6 cm 2 … 6 dm 2
We know that square decimeters are larger than square centimeters, and the numbers for these names are the same, which means we put the sign “<».
6 cm 2< 6 дм 2
Let's look at the third line.
95cm 2…9 dm
Please note that area units are written on the left, and linear units on the right. Such values cannot be compared (Fig. 5).
Rice. 5. Different sizes
Today in the lesson we got acquainted with another unit of area, the square decimeter, we learned how to convert square decimeters into square centimeters and compare values.
This concludes our lesson.
Bibliography
- M.I. Moreau, M.A. Bantova and others. Mathematics: Textbook. 3rd grade: in 2 parts, part 1. - M.: “Enlightenment”, 2012.
- M.I. Moreau, M.A. Bantova and others. Mathematics: Textbook. 3rd grade: in 2 parts, part 2. - M.: “Enlightenment”, 2012.
- M.I. Moro. Mathematics lessons: Methodological recommendations for teachers. 3rd grade. - M.: Education, 2012.
- Regulatory document. Monitoring and evaluation of learning outcomes. - M.: “Enlightenment”, 2011.
- “School of Russia”: Programs for primary school. - M.: “Enlightenment”, 2011.
- S.I. Volkova. Mathematics: Test work. 3rd grade. - M.: Education, 2012.
- V.N. Rudnitskaya. Tests. - M.: “Exam”, 2012.
- Nsportal.ru ().
- Prosv.ru ().
- Do.gendocs.ru ().
Homework
1. The length of the rectangle is 7 dm, the width is 3 dm. What is the area of the rectangle?
2. Express these values in square centimeters.
2 dm 2 = ... cm 2
4 dm 2 = ... cm 2
6 dm 2 = ... cm 2
8 dm 2 = ... cm 2
9 dm 2 = ... cm 2
3. Express these values in square decimeters.
100 cm 2 = ... dm 2
300 cm 2 = ... dm 2
500 cm 2 = ... dm 2
700 cm 2 = ... dm 2
900 cm 2 = ... dm 2
4. Compare the values.
30 cm 2 ... 1 dm 2
7 cm 2 … 7 dm 2
81 cm 2 ...81 dm
5. Create an assignment for your friends on the topic of the lesson.
Lesson objectives: introduce students to a new unit of measurement of area - the square decimeter.
Tasks:
- Introduce the concept of “square decimeter”, give an idea of the use of the new unit of measurement, its connection with the square centimeter.
- Develop logical thinking, attention, memory, observation; Computational skills; Length and area measurement skills.
- Develop the ability to work in pairs, perseverance, and accuracy.
DURING THE CLASSES
1. Communicating the topic and purpose of the lesson
– To find out what we will be working on today, complete the warm-up tasks. Find the odd one in each group and choose the corresponding letter.
P) 3, 5, 7
P) 16, 20, 24
C) 28, 32, 36
K) 5 + 5 + 5
L) 5 + 23 + 8
M) 23 + 23 + 8
3) Choose a solution to the problem: “36 tits flew to the feeder, nuthatches 9 times less. How many nuthatches have arrived?
ABOUT) 36: 9
P) 36 – 9
P) 36 + 9
H) RECTANGLE
W) SQUARE
SCH) TRIANGLE
A) KG
B) MM
B) SM
D) (5 + 3) 2
D) (5 – 3) 2
E) 5 2 + 3 2
b) WHAT? TIMES MORE (x)
E) WHAT? TIMES MORE (:)
I AM IN? TIMES LESS (:)
- Read what word you came up with. (Square)
– Why do you think? (In previous lessons we learned to calculate the area of shapes)
– Let’s continue this work and get acquainted with the new unit of measurement of area.
– What figure area do we already know how to calculate?
– Name the unit of measurement for area.
II. Updating knowledge
1) Mathematical dictation
- Calculate the product of numbers 4 and 8
- Increase the number 8 by 6 times
- Reduce the number 40 by 4 times
- The tailor made 7 identical suits from 14 meters of fabric. How many meters of fabric were needed for each suit?
- What number must be tripled to make 15?
- What is the perimeter of a square whose side is 2 cm?
- How many cm are in 1 dm?
- To renovate the apartment, we bought 4 cans of paint, 3 kg each. How many kg of paint did you buy?
Answers: 32, 48, 10, 2m, 5, 8 cm, 10cm, 12 kg.
– What 2 groups can we divide our answers into? (Prime and named numbers; even and odd; single-digit and double-digit)
– Underline the named numbers. Among the named ones, name the odd one out. (12 kg)
2) Conversion of quantities
(Individual work at the board is carried out by 2 students)
– Now let’s check how the students performed the transformation of named quantities
1 cm = ... mm
1 dm = ... cm
1 m = ... dm
65 cm = ... dm ... cm
27 mm = … cm … mm
8 m 9 dm = … dm
– What is measured in these units? (length)
– What other units of measurement do you know? (Area units)
3) Solving problems to find the area of a rectangle and square.
There are shapes on the board (rectangles and squares).
- Let's remember the formulas for finding the areas of these figures.
(One of the students goes out and selects the necessary ones from the many formulas for finding the perimeter and area for rectangles and squares).
S rectangle = a x b
S square = a x a
P squared = a x 4
P rectangle = (a + b) x 2
– What unit of measurement of area do you know? (cm 2)
– What is a square centimeter? (This is a square whose side is 1 cm.)
– What is its area? (1 cm 2)
III. Update.
1) – Today we will continue to talk about the area of a rectangle and get acquainted with a new unit of measurement of area, a new measure.
Divide the numbers into 2 groups:
3 cm
2 dm
46
4 mm
100
18 cm 2
2 dm 2
18
(Numbers can be divided into named numbers and ordinary numbers, numbers indicating length, area)
– Read the units of area? (18 square centimeters, 2 square decimeters)
– What are the possible sides of a rectangle with an area of 18 sq.cm? (2 cm and 9 cm, 6 cm and 3 cm, 18 cm and 1 cm)
– Which unit of area are we already familiar with? (Square centimeter).
– Which unit of area from those mentioned have not yet been discussed in detail? (dm2)
– Try to formulate the topic of the lesson? (Let's get acquainted with the square decimeter)
– We will get acquainted with the square decimeter, find out how it is related to the square centimeter, and learn to solve problems using a new unit of area
- But let's remember how you can measure the area of a rectangle? (Divide into square centimeters using a palette; overlaying shapes; applying measurements; measure length and width and multiply the data).
2) Work in pairs
– Now you will work in pairs. There is an envelope with figures on your table. Take a green rectangle out of the envelope and find its area yourself.
- Let's remember what needs to be done for this? (Measure length and width, multiply length by width)
3 x 4 =12 sq. cm.
– We found out the area of the rectangle. It is equal to 12 sq.cm. In what units did we measure the area of this rectangle? (In sq.cm).
IV. New topic
1) Introducing the square decimeter
– Place a yellow rectangle in front of you and take a small square out of the envelope. What can you say about this square? (This measurement is 1 square centimeter)
– Try using this measure to measure the area of a rectangle. How will you do this? (Apply a square)
– What is the area of this rectangle? (We didn’t have time to find out)
- Why didn’t you have time, you have everything to measure, you worked in pairs, what happened? (The measure is small, but the rectangle is large, it takes a long time to lay it out)
– There is another measure in the envelope, a large one, try to measure with this measure. (Measurement fit 2 times)
– Why did you complete this task quickly? (The measure is large, it was easy to measure)
– Now, using a ruler, measure the sides of the large measure (10 cm)
– How else can we write 10 cm? (1 dm)
– So a large measure is a square with a side of 1 dm. Look in your notebook at the small square you drew. Compare with a large measure. Think and tell me what in mathematics we call a square with a side of 1 dm? (1 square decimeter).
2) Working with the textbook
– Read the explanation on page 14.
– Why did people need to use a new unit of measurement of 1 sq. dm, if they already had a unit of 1 sq. cm? (To make it more convenient to measure large figures or objects)
– What do you think, the area of what can be measured in dm 2? (Area of a textbook, notebook, table, blackboard).
3) The relationship between square dm and square cm.
– Let’s calculate how many square centimeters will fit in 1 square. dm. How can I do that? (Divide the large square by sq. cm and count; we know that the side of the large square is 10 cm, we can multiply 10 by 10).
– Some suggested dividing by square centimeters and counting. Let's try to do this.
– Try to count quickly. Which way is easier and faster? (Multiply 10 by 10)
- Do the math. (100 sq. cm)
1 sq. dm = 100 sq.cm
– So, what have we learned now? (How is sq. dm related to sq. cm)
V. Physical education minute
VI. Consolidation
– Now we will learn to solve problems using a new unit of area.
1) Problem P. 14, No. 3
– The height of the rectangular mirror is 10 dm, and the width is 5 dm. What is the area of the mirror?
– In what units are the height and width of the mirror measured? (in dm)
- Why? (Large mirror)
The student at the blackboard decides with an explanation.
2) Problem p. 14, No. 4 (Two students at the blackboard)
3) Solving examples (orally in a chain)
L – 9 x (38 – 30) = M – 8 x 7 + 5 x 2 =
O – 65 – (49 – 19) = C – 9 x 9 + 28: 7 =
D – 28 + 45: 5 = Y – 7 x (100 – 91) =
VII. Lesson summary
– Our lesson has come to an end.
– What topic were you working on?
– In what units is area measured?
– How many square CM are there in 1 square DM?
– What new things have you learned for yourself?
– What did you like to do the most?
– What were the difficulties?
VIII. Homework
– Review the new material and consolidate the ability to find the area of rectangles – p. 14, No. 2.
(primary school teacher, secondary school No. 17)Chuvashova Nina Aleksandrovna
PHYSICAL AND MATHEMATICAL SCIENCES
"SQUARE DECIMETER"
in mathematics in 3rd grade
Primary school teacher
Municipal educational institution Secondary school No. 17, Serpukhov
Math lesson script
using a media product.
Class. Third.
Subject. : Square decimeter. Explanation of something new.
Educational and methodological support. Traditional school. Moreau's mathematics.
Necessary equipment and materials for the lesson. Computer, multimedia projector, presentation screen, pen, pencil, notebook, ruler, squares.
Time of implementation of the lesson. 40 minutes.
Media product. Visual presentation of educational material.
(environment: Windows XP SP2 Pro, editor: POWER POINT)
Technological scenario. (sequential model)
Lesson objectives:
1. Introduce students to a new unit of area measurement for them - the square decimeter.
2. Strengthen the ability to find the area of a rectangle and square
3. Improve mental calculation skills, knowledge of the multiplication table, and the ability to solve simple and compound problems.
4.Develop attention, intelligence, ingenuity.
5. Foster discipline and independence.
During the classes:
1.Communication of the topic and purpose of the lesson SLIDE 2
Stage 1 of the lesson. Self-determination for activity (organizational moment).
The purpose of the stage: creating an emotional mood for joint collective activities.
Forms, techniques, methods. Purpose of application.
1. Children’s psychological mood for the lesson
Math lesson begins.
Guys, show me what mood you are in before class?
(On the table each child has cards with a picture of the sun, the sun behind a cloud and clouds.)
And today I am in a joyful mood, because we are setting off with you on another journey through the Great Country of Mathematics. Good luck and new discoveries!
Znayka will accompany us on the journey.
Znayka and I, we are glad to meet you, friends!
And we think it was not in vain that we met.
We will learn today to decide
Research, compare, reason.
Znayka suggests doing a warm-up
"GYMNASTICS FOR THE MIND"
What date is today?
Increase it by 17.
How many dm are there in 1 m?
What number comes after 59,88,99?
Magnify 9 by 6 times
Increase 9 by 6
Reduce 42 by 7
Reduce 42 by 7 times
How many cm are in 1 m?
How many cm in 1d m? Activation of students' mental activity.
Stage II of the lesson. Updating knowledge.
Goal of the stage: development of skills to group figures, justify your opinion
Znayka's next task. Slide 3
The children have geometric shapes on the board and on their desks.
What figures are missing here? (1 and 3)
Why?
(Figures 2,4,5 have right angles, opposite sides, equal in pairs, they are rectangles).
Find its area of rectangle 2.
What do you need to know for this?
Is there a square among the rectangles? (Yes).
Name it (5).
What main property of a square do you know? (all sides are equal).
Measure the side of the square in front of you.
What is its area? (1 cm2)
Who thinks the same?
Development of students’ logical thinking, ability to compare and
analyze
III stage of the lesson. Statement and solution of a problem situation.
The purpose of the stage: to repeat the material and prepare students to learn new material.
Znayka has prepared a figure for you, it is on your desk. Slide 4
Measure the sides of this figure (10cm) click
What can we say? (this is a square, with a side of 10 cm)
- 10 cm is a linear unit, a unit of length.
Let us replace it with the largest linear unit.
10 cm = 1 dm click entry in notebook
- So you have a square with a side of 1 dm.
- how to find the area of this square? (Length times width)
click
S=1 dm * 1 dm = 1 dm2 notebook entry
-
this is a new unit of area measurement - 1 DM click
SQUARE DECIMETER
We found the area of the square in decimeters.
Turn your square over. What did you see? (divided by cm2)
How many squares can be laid in 1 dm2
How to find the area of this square?
(Count all the squares, count the squares by length and width and multiply them)
How to write this down?
S = 10 cm 10cm = 100 cm2 notebook entry
Which way is shorter?
In what units is area measured?
How many square centimeters are in 1 dm2? CLICK
.
- in 1 dm2 = 100 cm2 - write in a notebook
Who doesn’t understand what? Development of cognitive activity.
Developing the ability to make inferences based on previously acquired knowledge.
Physical exercise.
Goal: to avoid overload and fatigue of students, to maintain learning motivation.
"Calm"
The teacher speaks the words and the children perform the actions. Reflecting the meaning of words.
Everyone chooses a comfortable sitting position.
We are happy, we are having fun!
We laugh in the morning.
But then the moment came,
It's time to get serious.
Eyes closed, hands folded,
The heads were lowered and the mouth was closed.
And they fell silent for a minute,
So as not to hear even a joke,
So as not to see anyone, but
And only myself!
IV stage. Primary consolidation
Purpose of the stage: repeat the algorithm for finding the area.
Znayka has prepared the following task for you.
Open the textbook p.60, No. 3 slide 8
Finding the area of a mirror
- The length of the rectangular mirror is 10 dm, and the width is 5 dm. What is the area of the mirror?
Read the problem.
-What will we measure?
In what units are the length and width of the mirror measured? (in dm)
What is known?
What length?
What is known?
What's the Width?
What do you need to find?
How to do it?
As the task is analyzed, the data is displayed on the screen by clicking it.
Write down the solution yourself
1 student on the back of the board
S = 10 5 = 50 (dm 2)
Answer: 50 dm 2.
V-th stage of the lesson. Independent work with self-test
The purpose of the stage: consolidation of the studied material..
Znayka has prepared a task for you. Slide 9
Read the problem.
Draw a rectangle with sides 1 dm and 3 cm.
Find the area.
-What need to do?
-What is known?
- What length? Width?
-What units are length and width measured in?
(Different: dm and cm)
-What do you need to find? (find area)
Can I do it right away? (No)
What should you do first? (Convert dm to cm)
Make a plan to solve the problem.
1. Convert to dm to cm
2. Find the area
3. Write down the answer
Decide on your own according to the plan.
self-test from slide
Who hasn't made a single mistake?
Formation of practical skills in finding area
VIth stage of the lesson. Inclusion in the knowledge system and repetition.
The purpose of the stage: to develop skills in solving problems to repeat and consolidate the studied material.
Znayka has prepared a short note for you.
Create a task based on it.
Length 8 dm
Width-? 2 times less
Find S.
Can we immediately answer the question of the problem? Why?
Who can explain her decision?
(1 child at the board explains the solution to the problem and writes it down.)
independently using cards
(Solution of examples according to options,
followed by self-test
(control sheet on slide)
8 7 + 5 6
9 9-28: 7
63: 7 + 54: 6
9 (38-30)
65-(49-19)
28 + 45: 5
8 8
56: 8
49: 7
Who hasn't made a single mistake?
Helps develop skills to establish cause-and-effect relationships.
Application of previously acquired knowledge in practice.
Updating the acquired knowledge.
VIIth stage of the lesson. Reflection on activity (lesson summary).
Purpose of the stage: Summarizing all the work. The assessment itself.
You worked very fruitfully in class today.
-Our lesson has come to an end.
-What topic were you working on?
In what units is area measured?
-How many square cm are in 1 square DM?
-What did you succeed the most?
-What can you praise yourself for?
-What didn’t work?
- Guys, since we have achieved the goal of our lesson,
then what mood are you in?
Homework: p.60, No. 2. Slide 11
Slide 12
Znayka and I want to tell you
The lesson is over and the plan is completed.
Thank you guys very much.
For working hard and together,
And the knowledge definitely came in handy for you
Thank you for the lesson!
Method of stimulation and motivation
Target: promote the development of the ability to find the area of geometric shapes using a square decimeter
Tasks:
Educational:
determine a visual image of a new unit of area - a square decimeter;
Educational:
establish the relationship between square centimeter and square decimeter as units of area
Educational:
learn to calculate the area of rectangular figures using a square decimeter
Planned results:
Hello guys, my name is Kristina Evgenievna, today we will have a mathematics lesson.
And first, let's answer the questions:
· How can you compare figures by area?
(on the “eye” and superimposing one figure on another)
What does it mean to measure the area of a figure?
(measure how many squares fit in it)
· What common unit of area do you know?
· Areas, what shapes can you find based on their lengths?
(Square, rectangle)
You answered all the questions very well. It was no coincidence that we remembered with you about named numbers, units of measurement of length and area, this knowledge will be useful to us in the lesson.
and now I’ll tell you a story. But first, tell me, guys, what holiday will we have this week? Are you already preparing gifts for your mother?
At school, all the students were preparing for the upcoming holiday, Mother's Day. Students of class 3A decided to make invitation cards for their mothers. To do this, they needed colored cardboard with sides of 6 and 9 centimeters. What is the area of the invitation card? (54 cm)
And the students of grade 3B decided to prepare a rectangular advertisement with sides equal to the width and height of the desk, 30 centimeters and 4 decimeters. What will its area be? and what size sheet of colored cardboard will they need?
Were you able to complete the task?
Why doesn't it work? What's the problem? (we don’t know how to count, it’s taking a long time).
It turns out? What is the problem?
A problematic situation arises - how to multiply 30 cm by 4 dm - the children do not know the methods of non-table multiplication (they just learned the table up to 9).
Can we find out the area of the figure in cm2?
What to do?
We need a different unit of measurement for area.
Which? The children will guess that it will be dm 2.
Guys, we have also prepared a figure for you, get it under No. 1
Measure the sides of this figure (10cm)
What can you say about her? (this is a square, with a side of 10 cm)
10 cm is linear unit, unit of measurement of length.
Let us replace it with the largest linear unit.
10 cm = 1 dm writing in a notebook
So you have a square with a side of 1 inch.
So, on your tables there is a square with a side of 1 inch. This is a new unit of measurement for area. Who guessed what it's called? (sq. dm)
How to find the area of this square? (Length times width)
S=1 dm * 1 dm = 1 dm 2 writing in a notebook
What is its area?
What discovery have we made now? (We found the area of the square in decimeters)
Formulate the topic and objectives of the lesson.
Let's return to the desired problem and solve it. Let's draw a conclusion according to the task.
To do this, they may suggest expressing 30 cm as 3 dm. And find the area of the figure.
Take the second square #2. What did you see? (divided by cm2)
How many squares can you fit in 1 dm 2
How to find the area of this square?
How to write this down?
S= 10 cm · 10 cm = 100 cm 2 writing in a notebook
Which way is shorter?
In what units is area measured? (in dm 2)
How many in 1 dm 2 square centimeters? (click)
IN 1 dm 2 = 100 cm 2
Paint one square centimeter green.
- Why did people need to use a new unit of measurement of 1 sq. dm, if they already had a unit of 1 sq. cm?
What objects can be measured using this yardstick? Look around and name such objects (the surface of a desk, table, book, notebook, etc.)
We have made another discovery.
Now let’s open the textbook on page 144 and complete tasks No. 351
For which segment can the length be specified differently? Prove your answer.
Download:
Preview:
Target: promote the development of the ability to find the area of geometric shapes using a square decimeter
Tasks:
Educational:
determine a visual image of a new unit of area - a square decimeter;
Educational:
establish the relationship between square centimeter and square decimeter as units of area
Educational:
learn to calculate the area of rectangular figures using a square decimeter
Planned results:
Hello guys, my name is Kristina Evgenievna, today we will have a mathematics lesson.
Updating students' knowledge. Motivation for activity.
And first, let's answer the questions:
- How can you compare figures by area?
(on the “eye” and superimposing one figure on another)
- What does it mean to measure the area of a figure?
(measure how many squares fit in it)
- What common unit of area do you know?
(cm 2)
- Areas of which figures can you find based on their lengths?
(Square, rectangle)
You answered all the questions very well,- It is no coincidence that we remembered with you about named numbers, units of measurement of length and area; this knowledge will be useful to us in the lesson.
and now I’ll tell you a story. But first, tell me, guys, what holiday will we have this week? Are you already preparing gifts for your mother?
At school, all the students were preparing for the upcoming holiday, Mother's Day. Students of class 3A decided to make invitation cards for their mothers. To do this, they needed colored cardboard with sides of 6 and 9 centimeters. What is the area of the invitation card? (54 cm)
And the students of grade 3B decided to prepare a rectangular advertisement with sides equal to the width and height of the desk,30 centimeters and 4 decimeters. What will its area be? and what size sheet of colored cardboard will they need?
Were you able to complete the task?
Why doesn't it work? What's the problem? (we don’t know how to count, it’s taking a long time).
Would you like to know how to complete this task?
It turns out? What is the problem?
A problematic situation arises - how to multiply 30 cm by 4 dm - the children do not know the methods of non-table multiplication (they just learned the table up to 9).
Can we find out the area of the figure in cm? 2 ?
No?
What to do?
We need a different unit of measurement for area.
Which? The children will guess that it will be dm 2 .
Guys, we have also prepared a figure for you, get it under No. 1
Measure the sides of this figure (10cm)
What can you say about her? (this is a square, with a side of 10 cm)
10 cm is linear unit, unit of measurement of length.
Let us replace it with the largest linear unit.
10 cm = 1 dm writing in a notebook
So you have a square with a side of 1 inch.
So, on your tables there is a square with a side of 1 inch. This is a new unit of measurement for area. Who guessed what it's called? (sq. dm)
How to find the area of this square? (Length times width)
S=1 dm * 1 dm = 1 dm 2 writing in a notebook
What is its area?
What discovery have we made now? (We found the area of the square in decimeters)
Formulate the topic and objectives of the lesson.
Let's return to the desired problem and solve it. Let's draw a conclusion according to the task.
To do this, they may suggest expressing 30 cm as 3 dm. And find the area of the figure.
Take the second square #2. What did you see? (divided by cm 2 )
How many squares can you fit in 1 dm 2
How to find the area of this square?
How to write this down?
S = 10 cm 10 cm = 100 cm 2 writing in a notebook
Which way is shorter?
In what units is area measured? (In dm 2 )
How much in 1 dm 2 square centimeters? (click)
In 1 dm 2 = 100 cm 2
Paint one square centimeter green.
Compare the measurements with each other. What can you say?
- Why did people need to use a new unit of measurement of 1 sq. dm, if they already had a unit of 1 sq. cm?
What objects can be measured using this yardstick? Look around and name such objects (the surface of a desk, table, book, notebook, etc.)
We have made another discovery.
Now let’s open the textbook on page 144 and complete tasks No. 351
For which segment can the length be specified differently? Prove your answer.
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