Buzz
Solving Grade 3 Math pages 22, 23, 24, 25 Workbook 2
Solution manual for pages 22, 23, 24, 25 of Grade 3 Math Workbook 2, Connecting Knowledge with Life:
Perimeter of triangles, quadrilaterals, rectangles, squares
Activity 1
1. Solve Exercise 1 Page 22 Math Textbook Grade 3
Problem: Calculate the perimeter of a triangle with side lengths:
a) 7 cm, 10 cm, and 14 cm.
b) 20 dm, 30 dm, and 40 dm.
c) 15 dm, 20 dm, and 15 dm.
Solution Guide: The perimeter of a triangle is the sum of the lengths of its three sides (in the same unit of measurement).
b) The perimeter of the triangle is:
20 + 30 + 40 = 90 (dm)
Answer: 90 dm.
c) The perimeter of the triangle is:
15 + 20 + 15 = 50 (dm)
Answer: 50 dm.
2. Solve Exercise 2 Page 22 Math Textbook Grade 3
Problem: Calculate the perimeter of a quadrilateral with side lengths:
a) 3 dm, 4 dm, 5 dm, and 6 dm.
b) 10 cm, 15 cm, 10 cm, and 15 cm.
Solution Guide: The perimeter of a quadrilateral is the sum of the lengths of its four sides (in the same unit of measurement).
a) The perimeter of the quadrilateral is:
3 + 4 + 5 + 6 = 18 (dm)
Answer: 18 dm.
b) The perimeter of the quadrilateral is:
10 + 15 + 10 + 15 = 50 (cm)
Answer: 50 cm.
3. Solve Exercise 3 Page 22 Math Textbook Grade 3
Problem: A robot uses flashing lights to decorate a boat as shown in the drawing. How long is the string of flashing lights in centimeters?
Solution Guide:
- Observing the picture, we see that the flashing lights are decorated around the quadrilateral boat. Therefore, to calculate the length of the string of flashing lights, we calculate the perimeter of the quadrilateral.
- The perimeter of a quadrilateral is the sum of the lengths of its four sides (in the same unit of measurement).
Answer:
The length of the string of flashing lights is:
25 + 40 + 25 + 60 = 150 (cm)
Answer: 150 cm.
Activity 2
1. Solve Exercise 1 Page 24 Math Textbook Grade 3
Problem: Number?
Solution Guide: To find the perimeter of a square, we multiply the length of one side by 4.
Answers:
2. Solve Exercise 2 Page 24 Math Textbook Grade 3
Problem: Calculate the perimeter of a rectangle with:
a) Length 6 cm, width 4 cm.
b) Length 8 m, width 2 m.
c) Length 15 dm, width 10 dm.
Solution Guide: To find the perimeter of a rectangle, add the length and the width (in the same unit of measurement) and then multiply by 2.
b) The perimeter of the rectangle is:
(8 + 2) x 2 = 20 (m)
Answer: 20 m.
c) The perimeter of the rectangle is:
(15 + 10) x 2 = 50 (dm)
Answer: 50 dm.
3. Solve Exercise 3 Page 24 Math Textbook Grade 3
Problem:
Do you know how many sticks Nam needs to form a square with each side consisting of 3 sticks as shown in the picture?
Guidance: The number of sticks needed to form a square = Number of sticks on one side of the square x 4.
Answer:
Each side of the square is formed by 3 sticks.
The number of sticks needed to form a square with each side consisting of 3 sticks is:
3 x 4 = 12 (sticks).
So Nam needs 12 sticks to form a square with each side consisting of 3 sticks as shown in the picture.
- See more: Solutions for exercises on pages 27, 28, 29 of Math 3 Workbook 2, the book Connect Knowledge with Life
Practice
1. Solve Exercise 1 on Page 25 of Math Grade 3 Workbook
Problem: Choose the perimeter of each shape.
Solution Guide:
- To calculate the perimeter of a rectangle, add the length and width (in the same unit) and then multiply by 2.
- To calculate the perimeter of a square, multiply the length of one side by 4.
Answers:
The perimeter of the pink rectangle is:
(8 + 5) x 2 = 26 (cm)
The perimeter of the square is:
7 x 4 = 28 (cm)
The perimeter of the blue rectangle is:
(5 + 10) x 2 = 30 (cm)
We connect as follows:
2. Solve Exercise 2 on Page 25 of Math Grade 3 Workbook
Problem:
Do you think Viet's calculation is correct or incorrect?
Solution: To find the perimeter of a rectangle, add the length and width (in the same unit of measurement) and then multiply by 2.
Answer:
Viet's method is incorrect because the length and width of the table top are not measured in the same unit.
The correct calculation is:
1 m = 100 cm
The perimeter of the table top rectangle is:
(100 + 40) x 2 = 280 (cm)
3. Solving Exercise 3 on Page 25 of Grade 3 Math Textbook
Problem: Farmer Bac is building a fence around a rectangular vegetable garden with a length of 9 m and a width of 5 m. He leaves a 2 m wide gate for entry. How long is the fence?
Solution: The length of the fence = perimeter of the rectangular garden - 2 m.
Answer:
The perimeter of the vegetable garden is:
(9 + 5) x 2 = 28 (m)
The length of the fence is:
28 - 2 = 26 (m)
The answer is 26 m.
Solving exercises on pages 22, 23, 24, 25 of Grade 3 Math Book Volume 2, the book 'Connecting Knowledge with Life' will certainly be very helpful. Students and parents alike, refer to more materials to teach Math to children.
