Multiple choice

A boat takes half the time in moving a certain distance downstream than upstream. The ratio of the speed of boat in still water and that of the current is:

  1. $2 : 1$
  2. $4 : 3$
  3. $1 : 2$
  4. $3 : 1$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let boat speed = b and current speed = c. Downstream: time = d/(b+c). Upstream: time = d/(b-c). Given d/(b+c) = 0.5 × d/(b-c). Solving: 2/(b+c) = 1/(b-c), so 2(b-c) = b+c, giving b = 3c. Ratio is 3:1.

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