Question

A motorcyclist drives from place A to B with a uniform speed of 30 km/h and return from place B to A with a uniform speed of 20 km/h.Find its average speed. Sir / mam i don't understand from where 2 ×20×30/30+20 it is ?

Answer 1

Answer:

24m/sec

Explanation:

let

distance between A and B be X

time taken by the motorcyclist to travel a to b, =

$(t1) = \frac{distance}{speed2} \\ = \frac{x}{30}$

and time taken to travel by the motorcycle is to b to a =

$(t2) = \frac{distanc}{speed \: 2} \\ = \frac{x}{20}$

NOW

$average \: speed = \frac{total \: distance}{total \: time \: taken}$

$avg \: speed \: = \frac{x + x}{ \frac{x}{30} + \frac{x}{20} } \\ \\ = \frac{2x}{ \frac{5x}{60} } = \frac{2x \times 60}{5x} = 2 \times 12 \\ \\ \\ \\ = 24m {s}^{ - 1}$