It remains same

[sanju09]

A 20 litre mixture of milk and water contains milk and water in the ratio 3 : 2. 10 litres of the mixture is removed and replaced with pure milk and the operation is repeated once more. At the end of the two removal and replacement, what is the ratio of milk and water in the resultant mixture?

A. 17 : 3
B. 9 : 1
C. 3 : 17
D. 5 : 3
E. It remains same

[Rag_gmat]

3:17

[DanaJ]

You have an initial 20 l of mixture with 3:2 milk : water. This means that you initially have 12 l of milk and 8 l of water. Taking out 10 l leaves a mixture with the same ratio, but with 6 l milk and 4 l water. Add another 10 l and you get a mixture of 16 l milk and 4 l water. Remove 10 l of this one and you get that this particular mixture has 8 l milk and 2 l water. Add another 10 l of milk and final thing has 18 l milk and 2 water, making the desired ratio 9:1.

Answer B

[marcusking]

A 20 litre mixture of milk and water contains milk and water in the ratio 3 : 2. 10 litres of the mixture is removed and replaced with pure milk and the operation is repeated once more. At the end of the two removal and replacement, what is the ratio of milk and water in the resultant mixture?

A. 17 : 3
B. 9 : 1
C. 3 : 17
D. 5 : 3
E. It remains same

Initially there are 12L of Milk to 8L of water. If we remove 10 L of the mixture we remove half of each.

We now have 6L of Milk and 4L of water, now we add in 10L of milk for a new mixture of 16L Milk and 4L of water. We again take 10 L of the mixture so remove half of each ingredient (we reduce the total volume by half)

We now have 8L Milk and 2L of water. Again add 10 L of milk for final mixutre of 18L Milk and 2L of water.

18 : 2 == 9 : 1. B

[mygmat.2009]

Original mixture:
-------------------
M = 3/5 * 20 = 12 litres of milk
W= 2/5 * 20 = 8 litres of water

First replacement:
---------------------
Half of everything ==> 6 liters of milk + 4 litres of water
Add 10 litres of milk ==> 16 litres of milk + 4 litres of water

Second replacement:
---------------------
Half of everything ==> 8 liters of milk + 2 litres of water
Add 10 litres of milk ==> 18 litres of milk + 2 litres of water



Cheers,
Sam

[krisraam]

20 liters at 3:2 means 12 lits of milk and 8 litrs of water.

When 10 lits is taken that leaves 6 lits of milk and 4 lits of water( the ratio still remains same).

by adding 10 lits of milk the ratio is 16:4;

when 10 lits is taken that leaves 8 milk and 2 water.

By adding 10 more gives 18:2

ie 9:1

Thanks
raama