Aptitude - Alligation or Mixture - Discussion

Your logic is good Now, I can understand the solution. Thanks @Krishna.

@Munna: Here the key is every time we are removing same 4 L from the 40 L of mixture which constitutes to 10% of entire solution.

Hence the percentage remains constant.

It compare with the basic formula, to calculate the amount in case of Simple interest but here rate is negative.

It is more or less analogous to that.

There are 40 litres of milk in the container.
Now, 4 litres of milk is taken out and replaced by water.
So milk left in the mixture is 40-4=36 litres in the container.

Now this process is repeated twice:

Means again 4 litres of mixture (Milk + Water) is taken out from the container and replaced by water.
=> In the container, the mixture is in the ratio 36:4.

So, 4 litres of mixture that is to be replaced contains 4*(36/40) = 3.6 litres (parts of milk).
Now Total milk taken out after this process = 4+3.6 = 7.6 litres.
=> Now the mixture left in the container is 36-3.6 (parts of milk) : 8 (parts of water).
= 32.4 : 8.

Now again this process is repeated for the last time.
So 4 litres of mixture is taken out, this 4 litres contains => 4*32.4/40 = 3.24 (parts of milk).
Total milk parts taken out in the whole process = 7.6+3.24 = 10.84.
Now total milk left in the mixture (container) = 40-10.84 = 29.16.

Thanks @Bhargava reddy.

Thanks for the given explanation.

Thanks @MANOJ KUMAR.

Thanks for explaining the answer.

Suppose a container contains x of liquid from which y units are taken out and replaced by water.

After n operations, the quantity of pure liquid =x(1 -(y-x )power n)) units.

Thanks @Ajay.