Solving exercise 1 on pages 124-125 Math textbook Grade 5

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Ngày cập nhật gần nhất: 15/4/2026

Solving exercise 1 on pages 124-125 Math textbook Grade 5 in Practice section, Write the appropriate numbers in the blanks

Guidance to solve exercise 1 on pages 124-125 Math textbook Grade 5

Exercise:
Dung calculates 15% of 120 mentally as follows:
10% of 120 is 12
5% of 120 is 6
So, 15% of 120 is 18.
a) Write the appropriate numbers in the blanks to find 17.5% of 240 using Dung's method:
....% of 240 is...
...% of 240 is...
...% of 240 is...
So, 17.5% of 240 is...
b) Calculate 35% of 520 and explain the method.

Solution method:
Mental calculation:
- Observation: 15% = 10% + 5%
+ Calculate 10% of 240: Divide 240 by 10
+ Calculate 5%: Take 10% of 240 and divide by 2
+ Calculate 15% of 240: Take 10% of 240 and add 5% of 240.
=> Similar calculations for other questions.

Answer:
a) 10% of 240 is 24
5% of 240 is 12
2.5% of 240 is 6
So, 17.5% of 240 is 42.
b) We have 35% = 30% + 5%
10% of 520 is 52. So:
30% of 520 is 52 multiplied by 3 = 156
5% of 520 is 52 divided by 2 = 26.
So, 35% of 520 is 156 plus 26 equals 182.

Here is the solution guide for exercise 1 on pages 124-125 Math textbook. Additionally, there are 2 other exercises: exercise 2 on pages 124, 125 Math textbook Grade 5 and exercise 3 on pages 124, 125 Math textbook Grade 5. Let's explore the Solving Math Grade 5 pages 124, 125 guide to excel in Math Grade 5!

Frequently Asked Questions

What is the method used to calculate 17.5% of 240?

To calculate 17.5% of 240, first find 10% of 240, which is 24. Then, calculate 5% by dividing 10% by 2, resulting in 12. Finally, add 10% and 5% together: 24 + 12 = 36. Thus, 17.5% of 240 is 42.

How do you mentally calculate 35% of 520 using a specific method?

To calculate 35% of 520, first find 10% of 520, which is 52. Then, multiply 52 by 3 to find 30%, equaling 156. Next, calculate 5% by dividing 52 by 2, giving 26. Add 30% and 5% together: 156 + 26 = 182. Therefore, 35% of 520 is 182.

Why is understanding the calculation of percentages important in Grade 5 math?

Understanding percentage calculations is crucial in Grade 5 math because it builds foundational skills for more advanced math concepts. Mastering this helps students apply mathematical reasoning in real-life scenarios, enhancing their problem-solving abilities.

What steps should be followed to solve the exercises in the Grade 5 math textbook?

To solve the exercises in the Grade 5 math textbook, students should read the problem carefully, identify the percentage to be calculated, use mental math techniques like breaking down percentages into smaller parts, and then perform the calculations step by step to arrive at the final answer.

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