### Out of 20 boys, 6 are each of 1 m 15 cm height, 8 are of 1 m 10 cm and rest of 1 m 12 cm. The average height of all of them is :

A. 1 m 12.1 cm B. 1 m 21.1 cm C. 1 m 21 cm D. 1 m 12 cm Answer: Option A

### Solution(By Apex Team)

$\begin{array}{l}\text{According to the question,}\\ \text{Height of 6 persons}\\ \text{= 6 × 1 m 15 cm}\\ \text{6 m 90 cm}\\ \text{Height of 8 persons}\\ \text{= 8 × 1 m 10 cm}\\ \text{8 m 80 cm}\\ \text{Height of 6 persons}\\ \text{= 6 × 1 m 12 cm}\\ =\text{6 m 72 cm}\\ \text{Total Height of 20 persons}\\ \text{= 22 m 42 cm}\\ \text{Average}\\ =\Large\frac{22\mathrm{~m}42\mathrm{~cm}}{20}\\ =1\ \text{m}\ 12.1\ \text{cm}\end{array}$

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