A water tank is 3/8 full. After Joseph pours in 45 litres, it is 3/4 full. What is the capacity of the tank?

Question 30

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A water tank is $\frac{3}{8}$ full. After Joseph pours in 45 litres, it is $\frac{3}{4}$ full. What is the capacity of the tank?

40 litresCorrect answerYour answer60 litresCorrect answerYour answer120 litresCorrect answerYour answer360 litresCorrect answerYour answer

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CorrectNot quiteAnswer C

Correct answer: C

The 45 litres filled $\frac{3}{4} - \frac{3}{8} = \frac{6}{8} - \frac{3}{8} = \frac{3}{8}$ of the tank.
Capacity $= 45 \div \frac{3}{8} = 45 \times \frac{8}{3} = 120$ litres.

Worth noting

Treating 45 litres as $\frac{3}{4}$ of the tank gives 60 litres; the 45 litres is only the change from $\frac{3}{8}$ to $\frac{3}{4}$ .

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