Question

A motorcyclist drives from A to B with a uniform speed of 45 km/h and returns with a speed of 15 km/h. Find its average speed.

Answer 1

Motorcycle moves from A to B with a speed of 45 km/hr and returns to same point with uniform speed of 15 km/hr.

To find:

Average Speed of Motorcycle

Calculation:

$avg. \: v = \dfrac{total \: distance}{total \: time}$

$= > avg. \: v = \dfrac{2s}{ \dfrac{s}{45} + \dfrac{s}{15} }$

Cancelling the "s" term , we get :

$= > avg. \: v = \dfrac{2}{ \dfrac{1}{45} + \dfrac{1}{15} }$

$= > avg. \: v = \dfrac{2}{ \bigg(\dfrac{1 + 3}{45} \bigg)}$

$= > avg. \: v = \dfrac{2 \times 45}{4}$

$= > avg. \: v = 22.5 \: km {hr}^{ - 1}$

So final answer is :

Average Speed = 22.5 km/hr

Answer 2

Answer: 30 km / hr

Explanation:  Speed from A to B = 45 km / hr

                       Speed from B to A = 15 km / hr

Average speed = 45 + 15/ 2

                           = 60/2

                           = 30 km / hr

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