A dishonest milkman purchased milk at Rs. 66 per liter and mixes 9 liter water in it. He sold the mixture at Rs. 66 per liter and still he gains 33.33% profit. Find the quantity of milk bought by him.

27 Liters

33.33% profit ⇒ \(\frac{1}{3}\) = \(\frac{Water\;Qyt}{Milk\;Qty}\)

{***it is only applicable when mixture is sold at the cost price of milk}

        Milk  :  Water  ⇒ total mixture

Qty:   3    :     1     ⇒      4

1R = 9 liter

Milk= 3R = 3 × 9 = 27