Question

A person goes to certain distance at speed 4kmph. he returns on bicycle at the speed of 16kmph. find his average speed during the whole journey

Answer 1

Let the distance be x km

so, time taken to go the distance with speed 4kmph

= x/4 hr

so, time taken to return with speed 16kmph

= x / 16 hr

so, total time = x/4 + x/16 = 5x/16 hr

total distance = x + x = 2x

so, average speed = 2x / (5x/16)

= 32/5 = 6.4 kmph

Answer 2

Let the distance be x km

so, time taken to go the distance with speed 4kmph

= x/4 hr

so, time taken to return with speed 16kmph

= x / 16 hr

so, total time = x/4 + x/16 = 5x/16 hr

total distance = x + x = 2x

so, average speed = 2x / (5x/16)

= 32/5 = 6.4 kmph