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

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 what is the average height of all of them?
[A]1 m 12 cm
[B]1 m 12.1 cm
[C]1 m 21 cm
[D]1 m 21.1 cm

1 m 12.1 cm
Average height of all 20 boys =
$= \frac{6\times 1.15 + 8\times 1.1 + 6\times 1.12}{20}$
$= \frac{6.9+8.8+6.72}{20} = \frac{22.42}{20}$
= 1 m 12.1 cm
Hence option [B] is correct answer.