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 Examveda Team)

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