Question

On a 80 km staight road ,a bus travels the first 40km with uniform speed of 30km/h.how fast must the bus travel the next 40 km so as to have average speed of 40km/h for the entire trip?

Answer 1

Hi. .

Total distance =80km

Average speed of entire journey=40km/h

Total Time taken =
total distance/average speed

=80/40

=2hr.

Case :1.

Time taken to cover first 40km

Speed=30km/h

Distance=40km

T=distance/ speed=40/30

=1.3hr -----equation ( 1)

Case: 2.

Time taken to travel next 40km

Let speed be =Xkm/ h

X=40KM/t

t=40/X hours ----equation( 2)

Total time =1 +40/X

Since total time =2 hr

2 =1 +40/X

2-1 =40/X

1=40/X

X=40km/h

Therefore bus should travel next 40km distance at a speed of 40 km/h..

Hope this helps u!!