Question

a car travels a distance at a speed 30 km per hour and returns with speed of 40 km per hour calculate the average speed for the whole journey

Answer 1

2*30*40/70==240/7==34.2??

Answer 2

average speed=
$\frac{30 + 40}{2} \\ = \frac{70}{2}$
$= 35 \: km \: per \: hour$