Multiple choice

A boat covers 75 km downstream in 6 hours. If the speed of the current is (\frac{1}{5}) of its downstream speed, in what time will it cover a distance of 105 km upstream?

  1. 12 hours

  2. 15 hours

  3. 14 hours

  4. 18 hours

  5. None of these

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

Downstream speed = 75/6 = 12.5 km/h. Current speed = 1/5 of downstream = 12.5/5 = 2.5 km/h. Boat speed in still water = 12.5 - 2.5 = 10 km/h. Upstream speed = 10 - 2.5 = 7.5 km/h. Time for 105 km upstream = 105/7.5 = 14 hours.