A tank is half full. An inlet fills the whole tank in 10 minutes, and an outlet empties the whole tank in 6 minutes. Both are opened. How long does the tank take to empty?

3 minutesCorrect answerYour answer7.5 minutesCorrect answerYour answer8.5 minutesCorrect answerYour answer15 minutesCorrect answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer B

Correct answer: B

Net emptying rate $= \frac{1}{6} - \frac{1}{10} = \frac{1}{15}$ of the tank a minute.
Half a tank takes $\frac{15}{2} = 7.5$ minutes.

Worth noting

15 minutes is the time for a full tank.

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

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

Explanation