Question

a car covers 30 km at a uniform speed of 30 km per hour. what should be its speed for next 90 km if the average speed for the entire journey is 60 km per hour

Answer 1

Avg. Speed = 60 km/h

Time taken by car to cover 30 km= 30/30= 1 hr

Let the speed of car for next 90km be x

So, the time taken to complete 90 h = 90/x

Now, Avg. Speed = total distance/ total time taken

60 = 120/(1+(90/x))

60(x+90)= 120x

60x + 5400 = 120x

60x = 5400

x = 90 km/h (speed for next 90 km)