Multiple choice

Pipe A takes 10 minutes less than pipe B to fill a petrol tank, but takes 10 minutes and 25 seconds more than the two together. Find the time taken by pipe A alone to fill the petrol tank.

  1. 20 minutes

  2. 25 minutes

  3. 35 minutes

  4. 40 minutes

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

Let A take x minutes, B take x+10 minutes. Together they take 1/(1/x + 1/(x+10)) = x(x+10)/(2x+10). Given x = x(x+10)/(2x+10) + 10.416 (10m 25s). Solving this leads to x = 25.