Question

A man travels a certain distance at the rate of 10 km/h and returns to the same point at the rate of 15 km/h. his average rate for the whole journey is

Answer 1

Average speed when someone coverS the same amount of distances twice with different speed is given by

$averge \: speed = \frac{2 \times s1 \times s2}{s1 \: + s2}$

In this case, average speed is 12 km/h

$averge \: speed = \frac{2 \times 10\times 15}{10 + 15} = \frac{300}{25} = 12$