If a boat covers $160$ km downstream in half the time it takes to cover the same distance upstream, and it covers $96$ km downstream in $3$ hours, the stream speed is:

Question

If a boat covers $160$ km downstream in half the time it takes to cover the same distance upstream, and it covers $96$ km downstream in $3$ hours, the stream speed is:

Option A

4 km/h

Option B

6 km/h

Option C — Correct answer

8 km/h

Correct choice.

Option D

10 km/h

Explanation

Downstream speed $=96\div3=32$ km/h. Since downstream time is half upstream time for the same distance, upstream speed is $16$ km/h. Stream speed $=\frac{32-16}{2}=8$ km/h.

Chapter Mock 9: Boat and Stream