The average age of Raj and his sister is 8 years. If Raj’s age is 10 years, then find the age of his sister.

Correct option is C

Given:

Average = 8, Raj’s age = 10

Formula Used: 

Average = $$\frac{\text{Sum of age}}{\text{ total persons}}$$ ​​

Solution: 

​$$\text{Sum of ages = } 8 \times 2 = 16. \\ \ \\ \text{Sister's age = Sum - Raj's age.}$$​​

Sister's age = 16 - 10 = 6 yr

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