Three pumps, A, B, and C are capable of filling a reservoir. A fills in 5 hours, B in 7 hours, and C in 10 hours. When all three pumps are opened together, they operate for 1.5 hours before pump C is closed. How much additional time will it take to completely fill the reservoir after that?

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Accepted Answer

**Steps**

1. Find rates: $A=\frac{1}{5},\ B=\frac{1}{7},\ C=\frac{1}{10}$. Together rate $=\frac{31}{70}$.

2. Work in $1.5$ hours: $\frac{31}{70}	imes\frac{3}{2}=\frac{93}{140}$. Remaining $=1-\frac{93}{140}=\frac{47}{140}$.

3. After C closes, $A+B=\frac{12}{35}$. Time $=\dfrac{47/140}{12/35}=\dfrac{47}{48}$ hours.

FINAL_ANSWER: c

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