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 :

Answer: Option A

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