Multiple choice

The speed of a water boat against the stream is 6 km/h and with the stream is 9 km/h. Find the time taken by the boat to go to 30 km long way in still water and comeback to the same place.

  1. 6 hours

  2. 10 hours

  3. 8 hours

  4. 5 hours

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let boat speed = b and stream speed = s. Against stream: b - s = 6. With stream: b + s = 9. Adding: 2b = 15, so b = 7.5 km/h. In still water, time to go 30 km and return = 2 × 30/7.5 = 60/7.5 = 8 hours.