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Boats & Streams, Pipes & Cisterns · Question 77 of 85

Question 77

MediumOriginal question

A tank normally fills in 4 hours, but because of a leak at the bottom it takes 5 hours. How long would the leak take to empty the full tank?

Options for question 77

Show the answer and explanation
CorrectNot quiteAnswer D

Correct answer: D

Explanation

  1. Leak rate =14−15=120= \frac{1}{4} - \frac{1}{5} = \frac{1}{20} of the tank an hour.

  2. So the leak alone empties it in 20 hours.

Worth noting

1 hour is the delay the leak causes, not the time it takes to empty the tank.

Concept
The time a leak takes
Typical time
90 s
Your time
—
The rule this testsOutlets and leaks
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Ten questions from Boats & Streams, Pipes & Cisterns, at your own pace.

Practise this chapter →

Ten questions from Boats & Streams, Pipes & Cisterns, at your own pace.

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