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Jane took 30 min to drive her boat upstream to water-ski at her favorite spot. Coming back later in the day, at the same boat speed, took her 20 min. If the current in

that part of the river is 4 km per hr, what was her boat speed in still water?

Her boat speed in still water was km per hr.

Answer 1

The speed of the boat is 20 km/hr

Explanation:

Let s be the speed of boat in still water

Let d be the distance

Upstream speed = s-4

Jane took 30 min to drive her boat upstream to water-ski at her favorite spot.

So, Distance traveled in upstream =
`Speed * time =(s-4) * (30)/(60)`

Downstream speed = s+4

So, Distance traveled in downstream =
`Speed * time =(s+4) * (20)/(60)`

So,
`(s-4) * (30)/(60)=(s+4) * (20)/(60)`

30s-120=20s+80

10s=200

s=20

Hence The speed of the boat is 20 km/hr