In a bottle there is liquid A and B in the 7 5 ratio When 9 litres of the mixture is drained and 9 l...........

Quantitative Aptitude (CDS) Mixture and Alligation

In a bottle, there is liquid A and B in the 7:5 ratio. When 9 litres of the mixture is drained and 9 litres liquid B is filled then A: B become 7:9.Initial amount of A is?

21 litres

18 litres

12 litres

20 litres

Explanation:

A and B ratio is 7:5
let amount is 7x and 5x
(7x -9(7/12))/(5x +9(7/12)) =7/9
63x -(63)9/12=35x+9(49)/12
28x =9(49)/12 +(63)9/12
28x=9(112)/12
x=9(112)/12(28)
x=144/48
x=3
liquid A amount is 7(3)=21 litre