Question

A train travels some distance with a speed of 10m/s and returns along the same path with a speed of 15m/s. Calculate the average speed of the train.

Answer 1

Let the first distance travelled be A and the return distance be B

Speed with which the train travelled A=10m/s(v1)

Speed with which the train travelled B=15m/s(v2)

Here,distance travelled in both cases is same

Thus,average speed is 2v1v2/v1+v2

2×10×15/10+15

300/25

=12m/s

Answer 2

Answer:

Let the distance one way be ‘x’

Total distance be ‘2x’

t1 (time taken with 10 m/s ) = (x/10) * 60

t2 ( time taken with 10 m/s ) = (x/15) * 60

total time taken  = t1 + t2

= (x/10) + (x/15) = (3x + 2x / 30) = (5x / 30) 60

Avg. Speed = [(2x) / (5x)] / 30

(2x)(30) / 5x

60x / 5x = 12m/s

I think that should help!

Explanation: