Pipe A fills a tank in 6 hours and pipe B fills it in 9 hours. A drain C empties a full tank in 18 hours. With all three open on an empty tank, C is closed after 2 hours. How long does the whole filling take?

Answer and explanation

Correct answer: D. 4 hours in total

  1. Step 1: With all three open the net rate is of the tank per hour, so 2 hours fill .
  2. Step 2: Without C the rate is , and the remaining takes hours.
  3. Step 3: Add the phases: hours.
Answer
4 hours in total.
Why not the others: 4 hours 30 minutes forgets that C stops draining; 3 hours 20 minutes ignores the drain in the first phase; 5 hours keeps the drain open throughout.

Practise more Arithmetic, Algebraic Reasoning and Fractions.

Free questions with an explanation for every one, and full timed Qudurat GAT (Saudi Arabia) mock tests.

All Arithmetic, Algebraic Reasoning and Fractions questionsTake a mock test

More Arithmetic, Algebraic Reasoning and Fractions questions