Question

A motorcycle driver drive a cab with a uniform speed of $30$ km per hours and return back with the speed $20$ km per hours, find the average speed?

Answer 1

Let distance between a and b is t.
Time taken to go from a to b $=\frac{distance}{speed}$

$t_1=\frac{d}{30}$

time taken to return from b to a

$t_2=\frac{d}{20}$

total time $=\frac{d}{30}+\frac{d}{20}=\frac{2d+3d}{60}=\frac{5d}{60}$

Average speed

$=\frac{totaldis\tan ce}{totaltime}=\frac{d+d}{\frac{5d}{60}}$
$=\frac{2d\times 60}{5d}$

$=24\frac{km}{hrs}$