Allied & ICAR Exam Bank • ALLIED_2467 NAT • 2 Marks

Section 8: General Aptitude

Quantitative Aptitude

Subtopic: Numerical Computation

Question Statement:

A storage tank has 3 drain valves. Valves 1 and 2 open together empty it in 30 minutes; valves 2 and 3 empty it in 40 minutes; valves 1 and 3 empty it in 24 minutes. In how many minutes will all 3 valves open together empty the tank?

Answer Key:

20

Step-by-Step Solution & Explanation

$r_1 + r_2 = 1/30, r_2 + r_3 = 1/40, r_1 + r_3 = 1/24$. $2(r_1 + r_2 + r_3) = 1/10 \implies r_1 + r_2 + r_3 = 1/20$. Time = 20 minutes.
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