Question

a car travels from point A to B with a speed of 50 km per hour and return back to a from the with speed of 40 km per hour find average speed for per hour

Answer 1

let the distance be x then
Distance 1 = distance 2 = x

time 1 =distance/speed = x/50 and
time 2= x/40

average speed =
$\frac{d1 + d2}{t1 + t2}$
so,
$\frac{x + x}{ \frac{x}{50} + \frac{x}{40} }$
$\frac{2x}{ \frac{9x}{90} }$
$\frac{2x \times 90}{9x}$
$20$
that is the answer.

Answer 2

average = 50 km / hour
----------------
40 km / hour
therefore , km / hour is cancel and 50 / 40 and and is 5
--- and km per hour = km/ hour
4