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Step-by-step guide to solving Exercise 5 on page 28 of Math 5 textbook
Problem:
a) The average of two numbers is 9. If one of them is 12, find the other one.
b) The average of two numbers is 28. If one of them is 30, find the other one.
Solution Method:
* General Observations:
- The problem provides:
+ The value of the average of two numbers
+ The value of one of the numbers
- The problem requires: Find the other number.
* General Solution Approach:
- Let the unknown number be represented by a variable (x or y or z, ...)
- Apply the average calculation method: Average = (Unknown number + Known number) : 2
- Substitute the known values into the formula, transform it into a problem of finding the unknown (x or y or z, ...), calculate carefully to find the correct result.
Answers:
a) Let the unknown number be x.
According to the problem, we have: (x + 12) : 2 = 9.
So, the sum of the two numbers is: x + 12 = 9 x 2 = 18.
Therefore, the number to find is: x = 18 - 12 = 6.
Answer: x = 6.
b) Let the unknown number be y.
According to the problem, we have: (y + 30) : 2 = 28.
So, the sum of the two numbers is: y + 30 = 28 x 2 = 56.
Therefore, the number to find is: y = 56 - 30 = 26.
Answer: y = 26.
The solution to exercises on page 28 in Math 5 consists of 5 problems. After solving Exercise 5 on page 28 of Math 5 Practice, you can continue to explore hints and methods for Solving Exercise 1 on page 28 of Math 4, Solving Exercise 2 on page 28 of Math 4, Solving Exercise 3 on page 28 of Math 4, and Solving Exercise 4 on page 28 of Math 4 to improve your understanding of the subject.
