Question

Rahim while driving to school computes the average speed of his trip to be 20 km per hour on his returning trip along the same route there is less traffic and the average speed is 30 km per hour what is the average speed for Rahim strip

Answer 1

average speed = (total distance)÷(total time)

if the length of route is 'd km'
then total distance = 2d km
d/t1 = 20kmph
d/t2 = 30kmph

t1 = d/20
t2 = d/30

t1+t2 = 5d/60 = d/12

net average speed is
2d/(t1+t2)
= 24 kmph