Exams › SSC CGL (Prelims) › General
A 30-litre container of pure milk undergoes a 6-litre removal and 6-litre water replacement process, repeated 4 times. Approximately how much original milk remains?
- $15\frac{78}{125}$ litres
- $17\frac{28}{255}$ litres
- $12\frac{36}{125}$ litres
- $15\frac{68}{255}$ litres
Correct answer: $12\frac{36}{125}$ litres
Solution
In each operation, the fraction of milk left is $1-\frac{6}{30}=\frac{4}{5}$. After 4 repetitions, remaining milk = $30\left(\frac{4}{5}\right)^4 = 30\cdot\frac{256}{625} = 12.288$ litres, which is $12\frac{36}{125}$ litres.
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