Multiple choice

In one hour, a boat goes 11 km along the stream and 5km against the stream. The speed of boat in still water (in km/h) is:

  1. 3

  2. 5

  3. 8

  4. 9

  5. 10
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Downstream speed (u+v) = 11. Upstream speed (u-v) = 5. Still water speed u = (11+5)/2 = 8.

AI explanation

Using the boats and streams identity, the speed of the boat in still water is the average of its downstream and upstream speeds. The calculation is (11 + 5) / 2, which gives the speed of the boat in still water as 8 km/h.

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