Question

on a 60 km straight road a bus travela the first 30 kmwith a uniform speed of 30kmh-1 how fast much the bus travel the next 30 km so as to have average speed of 40kmh-1 for the entire trip​

Answer 1

Answer: This may help you

Explanation:

Given:

Total distance =60km

Average speed of entire journey=40km/h

Total Time taken =

total distance/average speed

=60/40

=3/2hr

Case :1

Let us CALCULATE time taken to cover first 30km

Speed=30km/h

Distance=30km

T=distance/ speed=30/30

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

Case: 2

Let us CALCULATE time taken to travel next 30km

Let speed be =Xkm/ h

X=30KM/t

t=30/X hours ----equation( 2)

Total time = add equation 1 and 2

=1 +30/X

Since total time =3/2 he

3/2 =1 +30/X

3/2-1 =30/X

1/2 =30/X

X=60km/h

Therefore bus should travel next 30km distance at a speed of 60 km/h

Answer 2

Avg speed of entire trip - V and total distance d=60Km and total time taken is t.

Avg speed in first 30Km _ v1=30Kmh-1 and time taken to cover it is t1.

Avg speed in last 30Km _ v2=? and time taken to cover it is t2.

V = d/t

V = 60/(t1+t2)

V = 60/[(30/v1)+(30/v2)]

40 = 60/[(30/30)+(30/v2)]

(30/30)+(30/v2) = 60/40 = 1.5

1 + (30/v2) = 1.5

30/v2 =0.5

v2 = 30/0.5

v2 = 60 Kmh-1