Question

13:A train travels from A to B at the rate of 20 km per hour and from
B to A at the rate of 30 km/hr. What is the average rate for the
whole journey?​

Answer 1

If distance is the same, the average speed can be calculated using the equation,

S = 2xy/(x+y) = 2*20*30/(20+30) = 1200/50 = 24 km/hr

The average speed of the journey = 24 km/hr

Answer 2

Answer:

24 km/h

Step-by-step explanation:

let distance be x km from A to B

journey from A to B

speed of train= 20 km/h

let time be t and distance x

we know

speed=distance/time

20=x/t

t=x/20

journey from B to A

speed of train=30km/h

let time be t' and distance is x km

we know

speed= distance / time

30=x/t'

t'= x/30

Now total time = t+ t'

=x/20+x/30= x/12 hours

Total distance travelled=x+x=2x km

Average speed = total distance traveled/total time taken

Average speed = 2x/(x/12)=(2x × 12)/x=24

Hence average speed of the train in whole journey is 24km/h