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Step-4

Title: Averages

Grade: 8-a Lesson: S3-L1

Explanation: Let us verify the answer here with the steps.

Description:

Step	Type	Explanation	Answer
1	Problem	The average age of brother and sister is 45. What is the sister’s age if the brother’s age is 50?
2	Hint	Formula used	\$"Average" = "sum of set of numbers" / "amount of numbers in set"\$
3	Step	The average age of sister and brother	45
4	Step	According to the formula	\$"Sum of their ages"/2 \$ = 45
5	Step	Multiply with 2 on both sides	\$\cancel2^1 \times ("Sum of their ages")/\cancel2^1 = 45 \times 2\$
6	Step	Sum of their ages	90 years
7	Step	Brother’s age	50
8	Step	Sister’s age	90 - 50 = 40
9	Step	Therefore, the Sister’s age is	40 years

Step

Type

Explanation

Answer

Problem

The average age of brother and sister is 45. What is the sister’s age if the brother’s age is 50?

Hint

Formula used

\$"Average" = "sum of set of numbers" / "amount of numbers in set"\$

Step

The average age of sister and brother

Step

According to the formula

\$"Sum of their ages"/2 \$ = 45

Step

Multiply with 2 on both sides

\$\cancel2^1 \times ("Sum of their ages")/\cancel2^1 = 45 \times 2\$

Step

Sum of their ages

90 years

Step

Brother’s age

Step

Sister’s age

90 - 50 = 40

Step

Therefore, the Sister’s age is

40 years