15 litres of mixture contains 20% alcohol and the rest water. If 2litres of water be mixed with it, the percentage of alcohol in the new mixture would be?  Choose the correct choice from the following options:
A) 16.67 %  B) 23 %  C) 18.3 %  D) 17.64 %  E) 21.23 %

Rationale: "alcohol in the 15 litres of mix . = 20 % of 15 litres = ( 20 * 15 / 100 ) = 3 litres water in it = 15 - 3 = 12 litres new quantity of mix . = 15 + 2 = 17 litres quantity of alcohol in it = 3 litres percentage of alcohol in new mix . = 3 * 100 / 17 = 17.64 % answer is d"
Answer: D