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There are two water tanks A and B. Tank A originally contain

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by Max@Math Revolution » Wed Aug 07, 2019 11:07 pm

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[GMAT math practice question]

There are two water tanks A and B. Tank A originally contains 100 liters of water and Tank B originally contains 20 liters of water. 5 liters of water is poured out of tank A every minute and, at the same time, 3 liters of water is poured into tank B every minute. How long will it take for the tanks to contain the same volume of water?

A. 10 min
B. 12 min
C. 15 min
D. 20 min
E. 22 min
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Source: — Problem Solving |

by swerve » Thu Aug 08, 2019 11:40 am
For Tank \(A\), we have
100 \(l\) - 5 \(l/min\)

For Tank \(B\), we have
20 \(l\) + 3\(l/min\)

Therefore,
\(100-(5/t) = 20+(3/t)\quad\Rightarrow\quad t = 10\, min\)
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by Max@Math Revolution » Sun Aug 11, 2019 11:49 pm
=>

The amount of water in the tank A after m minutes is 100 - 5m and the amount of water in the tank B after m minutes is 20 + 3m.
Equating these volumes yields 100 - 5m = 20 + 3m, or 8m = 80.
Thus, m = 10.

Therefore, A is the answer.
Answer: A
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