Question

From a container of milk, 5 litres of milk is replaced with 5 litres of water. This process is repeated again. Thus in two attempts the ratio of milk and water became 81 : 19. The initial amount of milk in the container was

A) 50 litres B) 45 litres C) 25 litres D) 20 litres

Answer 1

Answer:

Milk (Remaining)/ Water = 81/19.

Milk Remaining / Milk Initial = 81/100.

Therefore, Remaining Milk = Initial Concentration{1-(quantity taken out/ total amount)}^n

=> 81x = 100x(1-5/k)^2

=> 81/100 = (9/10)^2 = (1-5/k)^2

=> 1-5/k = 9/10

=> 5/k = 1-9/10 = 1/10

=> k= 50 litres.

so that 50 litres is your right answer.