### The average of 20 numbers is 12. The average of the first 12 numbers is 11 and that of the next 7 numbers is 10. The last number is ?

A. 40 B. 38 C. 48 D. 50 Answer: Option B

### Solution(By Apex Team)

$\begin{array}{l}\text{Let the last number = x}\\ \text{According to the question,}\\ \text{⇒ 12 × 11 + 7 × 10 + x = 20 × 12}\\ \text{⇒ 132 + 70 + x = 240}\\ \text{⇒ x = 240 – 202}\\ \text{⇒ x = 38}\end{array}$

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