In a certain boys camp, 20% of the total boys are from school A and 30% of those study science. If there are 63 boys in the camp that are from school A but do not study science then what is the total number of boys in the camp?  Answers: A) 70 B) 450 C) 150 D) 35 E) 350

Rationale: since 30 % of the boys from school a study science , then 70 % of the boys from school a do not study science and since 20 % of the total number of boys are from school a , then 0.2 * 0.7 = 0.14 , or 14 % of the boys in the camp are from school a and do not study science . we are told that this number equals to 63 , so 0.14 * { total } = 63 - - > { total } = 450 . answer : b .
Answer: B