A container contains 40 litres of milk. From this container 4 litres of milk was taken out and replaced by water. This process was repeated two more times. How much milk is now left in the container ?

29.16

The correct answer is option (3) : 29.16 litre

Given $x= 40\,  litre $

$y = 4\, litre $

$n= 3$

So, amount of milk left $= x(1-\frac{y}{x})^n$

$= 40(1-\frac{4}{40})^3$

$=40×(\frac{9}{10})^3$

$= 29.16\, litre $