Question

A motor boat can travel at 10 km/h in still water it travelled 91 km downstream in a river and then returned, taking altogether 20 hours find the rate of flow of river

Answer 1

Answer: 3 kmph

Explanation:

Answer 2

Hi Dear,

● Answer -

vs = 3 km/h

● Explanation -

Let vm be velocity of motoorboat and vs be velocity of river stream.

Velocity of boat upstream -

vu = vm + vs

Velocity of boat downstream -

vd = vm - vs

Total distance travelled when boat returns to origin -

t = s/(vm+vs) + s/(vm-vs)

20 = 91/(10+vs) + 91/(10-vs)

Solving this eqn,

vs = 3 km/h

Therefore, rate of river flow is 3 km/h.

Hope this helps..