Milk costs ₹50 a litre. In what ratio must water be mixed with milk so that the mixture costs ₹40 a litre?

Explanation

1. 01

   Water costs ₹0. Water : milk $= (50 - 40) : (40 - 0) = 10 : 40$.

2. 02

   That is $1 : 4$: one litre of water to every four of milk.