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GATE 2019 CE (CE2) – Question 9

General Aptitude · Quantitative Aptitude: Arithmetic and Number Computation · 2 marks · Multiple choice

Pipe X fills an oil tank in 5 hours and pipe Y in 4 hours, each alone. With the tank full and drainage open, it empties in 20 hours. Starting empty, both pumps run together while the drain stays open. Assuming head-independent drainage, find filling time (hours).

  1. 1.50
  2. 2.00
  3. 2.50
  4. 4.00

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Show answer and explanation

Correct answer: (C) 2.50

Explanation

Net filling rate is $1/5+1/4-1/20=0.4$ tank/hour. Required time is $1/0.4=$ **2.50 hours, C**.