Question

Q. 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
Option
a) 40% pure
b) 50% pure
c) 51.2% pure
d) none of these

Answer 1

let there be x amount of milk. by first replacement the milk is 80x/100. by second replacement the milk is 80x/100 × 80/100 i.e 64x/100 by third replacement the milk is 64x/100 × 80/100 which is 51.2%. hope it helps

Answer 2

C)51.2% is right answer

because

when we add water for first time

pure water % turns into 80%

and next time while adding water it changes into 64%

next into 51.2%