Question

80 litres of milk is kept in a container. From this volume, 8 litres of milk was taken out and replaced by water. This process was repeated two more times. How much milk (approximately) is now present in the container?

• A. 55 litres
• B. 58 litres
• C. 64 litres
• D. 75 litres
• E. 80 litres

Answer 1

The correct option is B

58 litres

Amount of liquid left after n operations, when the container originally contains x units of liquid from which y units is taken out each time is

$x{\left(\frac{x-y}{x}\right)}^n\text{units.}$

Thus, in the above case, the amount of milk left

$=80{\left[\frac{80-8}{80}\right]}^{3}litres=58.32litres$