Multiple choice

A boat covers 20 km in an hour with downstream and covers the same distance in 2 hours with upstream. Then, find the difference between the speed of boat and the speed of current?

  1. 5

  2. 10

  3. 15

  4. 12.5
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Downstream speed = distance/time = 20/1 = 20 km/h. Upstream speed = 20/2 = 10 km/h. Boat speed = (downstream + upstream)/2 = (20+10)/2 = 15 km/h. Current speed = (downstream - upstream)/2 = (20-10)/2 = 5 km/h. Difference = 15-5 = 10 km/h. Option A (5) is just the current speed, option C (15) is just the boat speed.

Keep practicing — related questions