Fresh grapes contain 90% by weight while dried grapes contain 20% water by weight. What is the weight of dry grapes available from 20 kg of fresh grapes?  Choose the correct choice:  A) 2 kg  B) 2.4 kg  C) 2.5 kg  D) 10 kg  E) none of these

Rationale: "the weight of non - water in 20 kg of fresh grapes ( which is 100 - 90 = 10 % of whole weight ) will be the same as the weight of non - water in x kg of dried grapes ( which is 100 - 20 = 80 % of whole weight ) , so 20 ∗ 0.1 = x ∗ 0.8 - - > x = 2.5 answer : c ."
Answer: C