Multiple choice general knowledge math & puzzles

A boat travels 20 kms upstream in 6 hrs and 18 kms downstream in 4 hrs.Find the speed of the water current?

  1. 1/2 kmph

  2. 7/12 kmph

  3. 5 kmph

  4. none of these

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

Upstream speed = 20/6 = 10/3 kmph (boat - current). Downstream speed = 18/4 = 9/2 kmph (boat + current). Solving: (b+c) - (b-c) = 2c, so 9/2 - 10/3 = 7/6, giving c = 7/12 kmph. The water current speed is 7/12 kmph, which is approximately 0.58 kmph.