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A 100-litre tank contains milk. 10 litres are drawn out and replaced with water. This is done 3 times. How much milk remains?
A$72.9$ litres
B$70$ litres
C$75$ litres
D$80$ litres
Answer & Solution
Correct answer: A. $72.9$ litres
After n replacements of x out of V: milk = V × (1 − x/V)^n = 100 × (0.9)³ = 100 × 0.729 = 72.9 litres.
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