### The average of ten numbers is 7. If each number is multiplied by 12, then the average of the new set of numbers is :

A. 7 B. 19 C. 82 D. 84 Answer: Option D

### Solution(By Apex Team)

Average of 10 numbers = 7 Sum of these 10 numbers = (10 × 7) = 70 \begin{aligned}&\therefore x_1+x_2+\ldots\ldots+x_{10}=70\\ &\Rightarrow12x_1+12x_2+\ldots\ldots+12x_{10}=840\\ &\Rightarrow\frac{12x_1+12x_2+\ldots\ldots+12x_{10}}{10}=84\\ &\text{⇒ Average of new numbers is 84}\end{aligned}

A. 20
B. 21
C. 28
D. 32

A. 18
B. 20
C. 24
D. 30

A. 10 years
B. 10.5 years
C. 11 years
D. 12 years