Question

A car travels a certain distance with a speed of 50 km per hr and returns with a speed of 40 km per hour. Calculate the average speed for the whole journey.​

Answer 1

Answer:

$\boxed{\bold{\mathsf{44.\overline{4}km}}}$/hr

Explanation:

Let the car travel t distance for reaching its destination and it travels the same distance in returning its starting point

So total distance = 2t

Using formula of time

$\boxed{\bold{\mathsf{Time = \frac{Speed}{Distance}}}}$

Car travels a certain distance with a speed = 50 km/hr

Time taken =

t/50

returns with a speed of = 40 km/hr

Time taken = t/40

Using formula:-

$\boxed{\bold{\mathsf{ Average\: Speed= \frac{Total\:distance}{Total\:time}}}}$

Putting in the values,

$\boxed{\bold{\mathsf{Average\: Speed= \frac{2t}{\frac{t}{50} + \frac{t}{40} }}}}$

$\implies{\bold{\mathsf{\frac{2t}{\frac{40t + 50t}{40\times 50} }}}}$

$\implies{\bold{\mathsf{\frac{2t \times (2000)}{90t} }}}$

$\implies{\bold{\mathsf{\frac{4000}{90}}}}$

$\boxed{\bold{\mathsf{44.\overline{4}km}}}$/hr