15 litres of mixture contains 20% alcohol and the rest water. If 5litres of water be mixed with it, the percentage of alcohol in the new mixture would be?	Choose the correct option
A) 16.67 %  B) 23 %  C) 15 %  D) 19.75 %  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 + 5 = 20 litres quantity of alcohol in it = 3 litres percentage of alcohol in new mix . = 3 * 100 / 20 = 15 % answer is c"
Answer: C