A container is full of milk. One-third of milk is taken out of it and replaced by same quantity of water. Then again one-third of the mixture is taken out of it and replaced by the same quantity of water. The process is repeated 4 times. If 16 litres of milk is left in the container at the end of 4th operation, find the capacity of the container.

Average no. of legs per head = (320 / 100) = (16 / 5)
or, 3 : 2
No. of goats = (3 / 3 + 2) × 100 = 60
No. of chickens = 100 ? 60 = 40.

Total quantity of iron = 4 (1 / 4) + 6 (2 / 3) = 1 + 4 = 5 kg.
Total quantity of tin = (4 + 6) ? 5 = 5 kg.
In the resultant mixture, iron : tin = 5 : 5 or 1 : 1

As per figure we can calculate the ration as below
Number of officers / Number of workers = 1000 / 7000 = 1 / 7
No. of officers = 1 / (1 + 7) × 400 = 50
No. of workers = 400 ? 50 = 350

According to figure we find that the ratio will be 3 : 1.

Quantity sold at 20% profit = 3 / (3 + 1) × 50 = 37.5 kgs.
Quantity sold at 40% profit = (50 ? 37.5) = 12.5 kgs.

Let cost price of spirit be Re. 1 per liter.
Then SP of mixture = Re. 1 per liter
Gain = 25%
So, CP of mixture = 1 × (100 / 125) = Re. 4 / 5
We assume that CP of water is zero.
Using allegation rule on cost price,
Water should be mixed to spirit in the ratio (1 / 5) : (4 / 5) or 1 : 4

Let the price per kg of mixed variety be Rs. P;
then By the rule of alligation,
Now, (20 - P) / (P - 15) = (2 / 3)
? 60 ? 3P = 2P ? 30
? 5P = 90
? P = Rs. 18

Let C.P. of 1 liter milk be Re. 1, Gain = 16 ²/₃ % = 50/3 %
and S.P. of 1 liter mixture = Re. 1
then C.P. of 1 liter mixture = (1 x (100 x 3) / 350) = Re. (6 / 7)
By the rule of alligation,
Hence, required ratio = (1/ 7) : (6 / 7) = 1 : 6

Here , Ratio of milk and water in mixture of 60 litre = 2 : 1
? Quantity of milk = 2y = 40 litre
Quantity of water = y = 20 litre
If ratio of milk and water is to be 1 : 2, then in 40 litres of milk, water should be 80 litre
? Quantity of water to be added = 60 litre.