Question

A car travels 100km at a speed of 60km/h and return with a speed of 40km/h.What is the average speed of the whole journey?

Answer 1

Hey

Total distance covered = 100 + 100

Total Time taken =

$\frac{100}{60} + \frac{100}{40}$

Average Speed =

$\frac{ \triangle x}{\triangle t} = \frac{100 + 100}{ \frac{100}{40} + \frac{100}{60} } = \frac{2}{ \frac{1}{40} + \frac{1}{60} }$

Thus, Average Speed = Harmonic Mean of two speeds = 48 kmph