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Step-4

Title: Averages

Grade: 8-a Lesson: S2-L3

Explanation: TODO

Description:

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?
Formula used	\$"Average" = "sum of set of numbers" / "amount of numbers in set"\$
Step - 1	The average age of sister and brother = 45
Step - 2	\$"Sum of their ages"/2 = 45\$
Step - 3	Multiply with 2 on both sides ⇒ \$\cancel2^1 \times ("Sum of their ages")/\cancel2^1 = 45 \times 2\$ Sum of their ages = 90 years
Step - 4	Brother’s age = 50
Step - 5	Sister’s age = 90 - 50 = 40 Therefore, the Sister’s age is 40 years.

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?

Formula used

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

Step - 1

The average age of sister and brother = 45

Step - 2

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

Step - 3

Multiply with 2 on both sides

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

Sum of their ages = 90 years

Step - 4

Brother’s age = 50

Step - 5

Sister’s age = 90 - 50 = 40

Therefore, the Sister’s age is 40 years.