Multiple choice

A boat can go 10 km downstream and 8 km upstream in 49 minutes. Also it can go 12 km downstream and 4 km upstream in 42 minutes. What is the speed of stream in km/h?

  1. 1.5

  2. 1

  3. 2

  4. 2.5
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let the downstream speed be d and the upstream speed be u. From the given conditions, we get the equations 10/d + 8/u = 49/60 and 12/d + 4/u = 42/60. Solving these equations gives d = 24 km/h and u = 20 km/h. The speed of the stream is half the difference of these speeds, which is (24 - 20)/2 = 2 km/h.

Keep practicing — related questions