capegemini - a milk can labelled p is filled with milk and water is mixed in the ratio 114 and another labelled q has mixture in ratio 32 in what ratio these two mixtures be mixed together to get a new one labelled r containing milk and water in the ratio 21 - skillgun

The c.p of milk be Re.1 per litre. ...(A)
Now, milk in 1 litre mixture of P = 11/15 ...(1)
Then c.p of 1 litre mixture of P = (11/15) x 1 = Re.11/15 (Based on value in previous equation and our assumption A)
Milk in 1 litre mixture of Q = 3/5 ...(2)
Then c.p of 1 litre mixture of Q = (3/5) x 1 = Re.3/5.As given in question, milk and water in final mixture are in the ratio 2:1. So Milk in 1 litre mixture of R = 2/(1 + 2) x 1 = 2/3. ...(3)
Then the c.p of 1 litre mixture of R = Re.2/3
Here, d = 11/15, c = 3/5 and m = 2/3
Then d - m = 11/15 - 2/3 = (11-10)/15 = 1/15
and m - c = 2/3 - 3/5 = (10-9)/15 = 1/15
Required ratio (as per our formula) = d-m : m-c = 1/15 : 1/15 = 1:1