Question

Distance between two places is 756 km a train covers the journey from places at 84 km per hour and returns back to a place with a uniform speed of 63 km per hour find the average speed of a train during the whole journey

Answer 1

here is ur answer

d=756km

v'=84km/hr

v"=63km/hr

Vavg=total distance/total time

Vavg=(756+756)/(t'+t")

[(t'=756/v');(t"=756/v")]

Vavg=1512/[(756/84)+(756/63)]

Vavg=(2×84×63)/(84+63)

Vavg=2×12×3=72km/hour.

method2

Vavg=(2×v'×v")/(v'+v")

is the general formula if distance travelled is same.

hope the answer is helpful.