A dishonest milkman wants to make a profit on the selling of milk. He would like to mix water (costing nothing) with milk costing Rs.33 per litre so as to make a profit of 20% on cost when he sells the resulting milk and water mixture for Rs.36 In what ratio should he mix the water and milk?
Choose the correct choice from the following choices: A) 1 : 20 B) 1 : 10 C) 1 : 8 D) 1 : 4 E) 6 : 11

Rationale: cost needed to net a 20 % profit : ( 36 - x ) / x = . 2 x = 30 actual cost : 33 solution ( x = liters of water needed to be added to the 1 liter of milk ) : 33 / ( 1 + x ) = 30 x = 1 / 10 so to get the cost down to 30 milk : water 1 : 1 / 10 or ( 10 / 10 ) : ( 1 / 10 ) answer : b
Answer: B