Aptitude - Alligation or Mixture - Discussion

Krishna. Your idea is good.

@Krisna

If in option there is 28.9 then what will you do?

The total quantity of milk is 40.

Case:1. 4 lit pure milk is taken out and 4 lit water is added.
Now we have a mixture of milk and water that contains
36 lit milk and 4 lit water.(milk:water=36:4=9:1 means
In 10 lit mixture there is 9 lit milk and 1 lit water)

Case:2. 4 lit mixture taken out (i.e. 36 lit mixture remains).

Our 40(or 10) lit mixture contains 4(or 1) lit water
and 36(or 9) lit milk.

so 4 lit mixture which is taken out, contains
4*4/40=0.40 lit water and
4*36/40=3.6 lit milk.

(i.e., 4 - 4*9/10 = 4 - 3.6 = 0.4 lit water and
4 - 4*1/10 = 3.6 lit milk taken out.)
so, remained 36 lit contains 36 - 3.6 = 32.40 lit milk
and 4 - 0.4 = 3.6 lit water.

Now 4 lit water is added.
so, water in 40 lit mixture after addition is
3.6 + 4 = 7.6 lit.

At the end of second case we get
milk : water = 32.40 : 7.60 = 8.10 : 1.90

Case:3. 4 lit mixture taken out (i.e. 36 lit mixture remained).

Our 40 lit mixture contains 7.60 lit water and 32.40
lit milk.
so 4 lit mixture contains 4*7.60/40=0.76 lit water and
4*32.40/40=3.240 lit milk.

(i.e., 4 - 4*8.1/10 = 4 - 3.24 = 0.76 lit water and
4 - 4*1.9/10 = 3.24 lit milk taken out.)
so, remained 36 lit mixture contains
32.40 - 3.24 = 29.16 lit milk and 7.60 - 0.76 = 6.84
lit water.


Now 4 lit water is added.
so, water in 40 lit mixture after addition is
6.84 + 4 = 10.84 lit.

At the end of third case we get
milk : water = 29.16 : 10.84

M.V. Krisna gave an excellent logic.

@ Krishna.

Your logic is correct but if its options are changed logically then your logic gets fail.

Please give a more suitable and simple explanation.

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 n units.

Thanks dilip I understood the solution very well.

Only 2 times is given in the question. How can you say the action was repeated thrice and cube that.

Hope guys. This will help you.

40-4 == taken out 10% milk == 36.

36-4 == taken out 10% milk == 32.40.

32.40 == taken out 10% milk == 29.16.

Why is 3 taken as the power whereas it should be 2 as its repeated two times. Someone please explain?