Of 600 surveyed students, 20% of those who read book A also read book B and 25% of those who read book B also read book A. If each student read at least one of the books, what is the difference between the number of students who read only book A and the number of students who read only book B? Choose the correct option
A) 20
B) 25
C) 30
D) 35
E) 75

Rationale: say the number of students who read book a is a and the number of students who read book b is b . given that 20 % of those who read book a also read book b and 25 % of those who read book b also read book a , so the number of students who read both books is 0.2 a = 0.25 b - - > a = 1.25 b . since each student read at least one of the books then { total } = { a } + { b } - { both } - - > 600 = 1.25 b + b - 0.25 b - - > b = 300 , a = 1.25 b = 375 and { both } = 0.25 b = 75 . the number of students who read only book a is { a } - { both } = 375 - 75 = 300 ; the number of students who read only book b is { b } - { both } = 300 - 75 = 225 ; the difference is 300 - 225 = 75 . answer : e .
Answer: E