Question

A car covers a distance in 40 minutes with an avarage speed of 60 km per hour . The avarage speed to cover the same distance in 30 minutes is?

Answer 1

Let the distance travelled be x km

Time taken = 40 minutes = 2/3 hrs

average speed = 60 km/hr (given)

we know that,

avg. speed = total distance/total time

so,

60 km/hr = x/2/3

or, 60km/hr = 3x/2

or, x = 60×2/3

or, x = 40 kms.

Again in second case

distance= 40 km ( same distance)

time = 30 mins. = 1/2 hrs.

and we know that,

avg speed= total distance/ total time

so, avg speed = 40 / 1/2 km/hr

or, avg speed = 40×2 km/hr

or, avg speed = 80km/hr

therefore, the required average speed

= 80 km/ hr