From a container having pure milk, 20% is replaced by water and the process is repeated thrice. At the end of… · ABC26GN2477
Subject: General Aptitude · Chapter: Percentage
From a container having pure milk, 20\% is replaced by water and the process is repeated thrice. At the end of the third operation, the milk is
(a)40\% pure
(b)50\% pure
(c)51.2\% pure
(d)58.8\% pure
Answer
Answer (as printed): C
Explanation
Let total quantity of original milk = 1000 gm. Milk after first operation $=80 \%$ of $1000=800 \mathrm{gm}$. Milk after second operation $=80 \%$ of $800=640 \mathrm{gm}$. Milk after third operation $=80 \%$ of $640=512 \mathrm{gm}$. ∴ Strength of final mixture = 51.2\%.
Explanation as extracted from the printed page; notation may be imperfect.