Question

A cistern has two taps which fill it in 12 minutes and 15 minutes respectively. There is also a waste pipe in the cistern. When all the pipes are opened, the empty cistern is full in 20 minutes. How long will the waste pipe take to empty a full cistern? (a) 8 minutes (b) 10 minutes (c) 12 minutes (d) 16 minutes

   A cistern has two taps which fill it in 12 minutes and 15 minutes respectively. There is also a waste pipe in the cistern. When all the pipes are opened, the empty cistern is full in 20 minutes. How long will the waste pipe take to empty a full cistern?
(a) 8 minutes
(b) 10 minutes
(c) 12 minutes
(d) 16 minutes

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The Pearson Guide to Objective Arithmetic for Competitive Examinations

The Pearson Guide to Objective Arithmetic for Competitive Examinations

Dinesh Khattar 2nd Edition

Chapter 14, Problem 19

Instant Answer

Step 1

- The first tap fills the cistern in 12 minutes, so its rate is \( \frac{1}{12} \) of the cistern per minute. - The second tap fills the cistern in 15 minutes, so its rate is \( \frac{1}{15} \) of the cistern per minute. Show more…

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A cistern has two taps which fill it in 12 minutes and 15 minutes respectively. There is also a waste pipe in the cistern. When all the pipes are opened, the empty cistern is full in 20 minutes. How long will the waste pipe take to empty a full cistern? (a) 8 minutes (b) 10 minutes (c) 12 minutes (d) 16 minutes

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