A milk vendor has 2 cans of milk. The first contains 25% water and the rest milk. The second contains 50% water. How much milk should he mix from each of the containers so as to get 12 litres of milk such that the ratio of water to milk is 3 : 5?

• A. 5 litres, 7 litres
• B. 7 litres, 5 litres
• C. 4 litres, 8 litres
• D. 6 litres, 6 litres

Answer: (D)

Let the cost of 1 litre milk be Re. 1 Milk in 1 litre mix. in 1st can = 3 litre, C.P. of 1 litre mix. in 1st can Re. 3 4 4 Milk in 1 litre mix. in 2nd can = 1 litre, C.P. of 1 litre mix. in 2nd can Re. 1 2 2 Milk in 1 litre of final mix. = 5 litre, Mean price = Re. 5 8 8 By the rule of alligation, we have: C.P. of 1 litre mixture in 1st can    C.P. of 1 litre mixture in 2nd can 3 4 Mean Price5 8 1 2 1 8 1 8 ∴ Ratio of two mixtures = 1 : 1 = 1 : 1. 8 8 So, quantity of mixture taken from each can = ❨ 1 x 12 ❩ = 6 litres.