Question

A car travels 30 km at uniform speed of of 40 kmph and the next at a uniform speed of 20 kmph . Find its average speed

Answer 1

Answer:

We know that,

Speed=Distance / time

.°. Time =dist / speed

Let's see the first case,

s = distance = 30 km

v = speed = 40 km/hr

t = time = 30 / 40

=3/4 hrs

Let's see the second case,

s = 30 km

v = 20 km/hr

t = 30 / 20

t = 3/2 hrs

Avg. Speed =Total distance/ Total time

=(30 + 30) / (3/4) + (3/2)

=60 / ( 3 + 6 ) /4

=60 / 9 × 4

=20 / 3 × 4

=80 / 3

=26.67 ( Approx. )

Hence,

Average speed of the car is 26.67 km/hrs ( Approx. )