CAT 2025 Slot 3 QA Q19 Time & Work

Question 19 of the Quantitative Ability (QA) section, CAT 2025 Slot 3, with CAT's official answer and a worked solution.

The rate of water flow through three pipes A, B and C are in the ratio 4 : 9 : 36. An empty tank can be filled up completely by pipe A in 15 hours. If all the three pipes are used simultaneously to fill up this empty tank, the time, in minutes, required to fill up the entire tank completely is nearest to
  1. A
    73
  2. B
    76
  3. C
    78
  4. D
    71

Answer: (A) 73 Time & Work MCQ

Solution

  1. Pipe A (4 parts) fills in 15 h, so 1 part fills \(\frac{1}{60}\) tank per hour.
  2. All three together: \(4 + 9 + 36 = 49\) parts \(= \frac{49}{60}\) tank per hour.
  3. Time \(= \frac{60}{49}\) h \(= \frac{3600}{49} \approx 73.5\) min, nearest 73.

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