A cask contains 125 litres of pure syrup. 25 litres are drawn off and replaced with water. This operation is performed three times in all. How much syrup remains in the cask?
Correct answer D. 64 litres
Explanation
Using the repeated replacement formula, syrup left = 125 x (1 - 25/125)^3 = 125 x (4/5)^3 = 64 litres.
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