Question

on a 60km straight road , a bus travel the first 30km with a uniform speed of 30km/h . how fast must the bus travel the next 30 km so as to have average speed of 40km/h for the entire trip ?

Answer 1

Hey.

Here is the answer.

Total distance = 60 km

distance travelled with 30kmph is 30 km

so, time taken = 30/30 = 1 h

Let he cover the rest 30 km with a speed of x kmph

So, time taken = 30/x h

As, total distance = 60 km

total time = 1 + 30/x

so, average speed = 60/(1 + 30/x)

or, 40 = 60x/(x+30)

or, 40x + 1200 = 60x

or, 20x = 1200

so, x = 60 kmph

Thanks .