If C.P. of 24 books is equal to S.P of 30 books , then your gain or loss is ? Choose one:
A) 23 1/3 gain %  B) 30 10/23 loss %  C) 20% loss %  D) 30 1/3 loss %  E) 40 1/3 loss %
Say the cost price of 24 books is $24 so $1 for a book.   The cost of 30 books would be $30, and the selling price of 30 books would be 24$, hence the loss = ($30 - $24)/$30 = 20%.   Answer: 20% loss %.
<result>C</result>
If C.P. of 24 books is equal to S.P of 30 books , then your gain or loss is ?