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Answer 1

Answer:

The speed of the boat is 20 km/hr

Step-by-step 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 =$Speed \times time =(s-4) \times \frac{30}{60}$

Downstream speed = s+4

So, Distance traveled in downstream = $Speed \times time =(s+4) \times \frac{20}{60}$

So, $(s-4) \times \frac{30}{60}=(s+4) \times \frac{20}{60}$

30s-120=20s+80

10s=200

s=20

Hence The speed of the boat is 20 km/hr