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Guide to solving Math 5 pages 79-80 - including solution methods
Problem:
a) Calculate 216.72 : 42;
b) Calculate 1 : 12.5;
c) Calculate 109.98 : 42.3;
Solution Method:
Review the division method as instructed in Exercise 1 on page 64 of the Math 5 Practice Textbook.
Answer:
2. Solve Exercise 2 - Solve Math 5 Concentrated Practice on pages 79, 80
Problem:
a) Calculate (131.4 - 80.8) : 2.3 + 21.84 x 2;
b) Calculate 8.16 : (1.32 + 3.48) - 0.345 : 2;
Solution Method:
Rules for performing multiple operations in an expression:
- Expression containing parentheses: Perform operations inside the parentheses first, then outside.
- Expression containing only addition and subtraction or only multiplication and division: Perform operations from left to right.
- Expression involving both multiplication/division and addition/subtraction: Perform multiplication/division first, then addition/subtraction.
Answer:
a) (131.4 - 80.8) : 2.3 + 21.84 x 2 = 65.68.
b) 8.16 : (1.32 + 3.48) - 0.1725
= 1.7 - 0.1725
= 1.5275.
3. Solve Exercise 3 - Solve Math 5 on pages 79, 80
Problem:
At the end of the year 2000, the population of a ward was 15,625 people. At the end of the year 2001, the population of that ward was 15,875 people.
a) How much percent did the population of the ward increase from the end of 2000 to the end of 2001?
Solution Method:
Students apply the following concepts:
- To find a% of b: Divide b by 100, then multiply by a or multiply b by 100 and divide by 100.
- To find the percentage ratio of two numbers: Divide the first number by the second number, multiply by 100, and add the % symbol to the result.
Answer:
a)
Method 1:
Compared to the population in 2000, the population in 2001 occupies a percentage of:
15875 : 15625 x 100% = 101.6%
From the end of 2000 to the end of 2001, the population of that ward increased by a percentage of:
101.6% − 100% = 1.6%
Method 2:
The population increase from the end of 2000 to the end of 2001 for that ward is:
15875 − 15625 = 250 (people)
So, from the end of 2000 to the end of 2001, the population of that ward increased by a percentage of:
250 : 15625 x 100 = 1.6%
b) The population increase from the end of 2001 to the end of 2002 for that ward is:
15875 : 100 x 1.6 = 254 (people)
The population of that ward in 2002 is:
15875 + 254 = 16129 (people)
Answer: a) 1.6%;
b) 16129 people.
4. Solve Exercise 4 on pages 79, 80 Math 5 Textbook
Problem:
Choose the letter before the correct answer:
A salesperson incurred a loss of 70,000 VND, and that amount is 7% of the invested capital. To calculate the invested capital, we need to calculate:
A. 70000 : 7
B. 70000 x 7 : 100
C. 70000 x 100 : 7
D. 70000 x 7
Solution Method:
To find the invested capital, we can take the loss amount and divide it by 7% (or equivalently, divide by 100, then divide by 7).
Answer:
To find the invested capital, we can calculate 70000 : 7 x 100 or 70000 x 100 : 7
Choose answer C
Quick Guide to Solving 5th Grade Math Pages 79 and 80
Solve Exercise 1 on page 79 of Math textbook for 5th grade
a) 216.72 : 42;
b) 1: 12.5;
c) 109.98 : 42.3
Answers:
a) 5.16; b) 0.08; c) 2.6
Solve Exercise 2 on page 79 of Math textbook for 5th grade
a) (131.4 – 80.8) : 2.3 + 21.84 x 2;
b) 8.16 : (1.32 + 3.48) – 0.345 : 2
Answers:
a) (131.4 – 80.8) : 2.3 + 21.84 x 2
= 50.6 : 2.3 + 43.68
= 22 + 43.68
= 65.68
b) 8.16 : (1.32 + 3.48) – 0.1725
= 1.7 – 0.1725
= 1.5275
Solve Exercise 3 on page 79 of Math textbook for 5th grade
At the end of the year 2000, the population of a district was 15,625 people. At the end of 2001, the population was 15,875.
a) How much percentage did the population increase from the end of 2000 to the end of 2001?
b) If from the end of 2001 to 2002, the population increased by the same percentage, then at the end of 2002, how many people were in the district?
Solution: a) Compared to the population in 2000, the population in 2001 was:
15,875 : 15,625 = 1.016 = 101.6%
The population of the district increased by:
101.6% – 100% = 1.6%
b) 1.6% of 15,875 people is:
15875 x 1.6 : 100 = 254 (people)
The population of the district in 2002 is:
15875 + 254 = 16,129 (people)
Answers: a) 1.6 people b) 16,129 people
In Chapter I, we familiarize ourselves with measurement units, with Hectare being widely used. Check out the hints for Solving 5th Grade Math Pages 29 and 30 to excel in the subject.
Solving problem 4 on page 80 of Math 5 textbook: A salesman incurred a loss of 70,000 VND, which is 7% of the amount spent. To calculate the capital of the person, we need to calculate:
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One of the most important topics in the Math 5 program is subtracting decimal numbers, which students need to review carefully.
Here is a suggestion for solving Math 5 page 79, 80, Centralized practice with full details. Prepare for the content of Centralized practice on page 80 of Math 5 textbook through the solution of exercises on page 80 of Math 5 textbook, Centralized practice, and the introduction of pocket calculators through the solution of exercises on page 82 of Math 5 textbook to study Math 5 better.
