Question

A bus travels one-third of distance with a velocity of 12km/h and remaining distance with 20km/h. Find its average speed

Answer 1

Let the distance be X.

1 / 3 x he covers using 12 km / h

Remaining = 2 / 3 km which he covers using 20 km / h

Lets take the distance x to be 1 then :

Time for the first portion will be:

T = Distance / speed

1/3 × 1/12 = 1/36 hrs

Second portion:

2 / 3 × 1/20 = 1 / 30 hrs

Average speed = total distance / total time

Total time = (1/36) + (1/30) = 0.3611 hrs

Average speed :

1 ÷ 0.3611

= 3 km / h (approx)