Aptitude - Alligation or Mixture - Discussion

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.

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.

Case 1: total milk = 40lits.
Case 2 : 4lits are replaced by water = 40 - 4 = 36lits of Milk.
So the total = 36lits of milk + 4lits of water.

Two times repeat again.
Case 3 : 36lits of milk-4lits of milk +4lits of water=32lits of milk +8lits of water =total 40lits of milk and water.

36lits of milk - 4lits of milk + 4lits of water = 28lits of milk - 4lits of milk +1 2lits of water
So total 28lits of milk and 12lits of water.

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

Simple: in question given he replace milk with water three times. Once he replaces then further repeat process two times.

40 litre milk ----> 4 litre milk removed (4 is 10% of 40) = 36 litre left.

Now again 4 litre milk removed (again 10% removed) from 36 litre mean 3.6 litre removed = 32.4 litre left.

Now again 4 litre removed = mean 10% of 32.4 is 3.24 so 3.24 litre remove and you left with 29.16 litre!

Best Answer @Manoj Kumar.

A venal contains a mixture of milk and water. Milk being 49% of the solution. Two times the mixture is taken out and replaced by water. Now the mixture contains only 9%of milk. How many litres of mixture is taken out?

Find the solution of the problem.

Given 40L milk.

Step1: 4L milk is replaced & 4L water is added, i.e. it now contains 40L mix of 36L M & 4L W in d ratio 9:1,

So even if you take 1L of the mix it will contain (9parts M & 1 part W) & this is repeated 2mor times.

So to calculate the amount of milk present :

1st time: 40 * 9/ (9 + 1 =10).

2nd time: 40 * (9/10) * (9/10), 3rd time: 40 * (9/10) * (9/10) * (9/10) = 29.16.

You are right @Manoj.

Must follow this to all this type of questions.

4 lit drawn then ratio: 4/40 => 1/10.
Rest liquid: 9/10.

Total : Rest
(10) power 3 : 9 power is 3

Ratio becomes 1000 : 729.

Now according to question 1000 : 40,
then,
1 : 0.04

Rest liquid 729=> 729 * 0.04=> 29.16.