A dishonest grocer professes to sell pure milk at cost price but he mixes it with water and thereby gains 25%. Find the percentage of water in the mixture assuming that water is freely available.

20%

   25% profit ⇒ \(\frac{1(water)}{4(milk) }\)

Milk      :        Water       :    total mixture

4          :           1           :            5

% of water in mixture ⇒ \(\frac{1}{5}\)  × 100 = 20%