# Pipes and Cisterns - Aptitude Questions and Answers Part 4

**16. Three inlets P, Q and R take 6 hours to fill a cistern. After being open for 2 hours together, inlet R develops a fault and has to be closed. P and Q fill the remaining cistern in 7 hours. How much time would R take to fill the cistern alone?**
a. 10 hours

b. 12 hours

c. 14 hours

b. 16 hours

**17. There are two taps to fill a tank. Pipe A is three times faster than Pipe B. Both the pipes opened together can fill the tank in 36 minutes. How long will the slower pipe take to fill the tank alone?**
a. 81 minutes

b. 108 minutes

c. 144 minutes

d. 192 minutes

**18. Pipe A can fill the tank in 60 minutes while Pipe B does it in 40 minutes. If the tank is empty and Pipe B is opened for the first half while both Pipe A and B are opened for the second half, how long will it take to fill the empty tank?**
a. 15 minutes

b. 20 minutes

c. 27.5 minutes

d. 30 minutes

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