If C.P. of 23 books is equal to S.P of 30 books , then your gain or loss is ?  Choose the correct choice
A) 23 1/3 gain %
B) 30 10/23 loss %
C) 23 1/3 loss %
D) 30 1/3 loss %
E) 40 1/3 loss %
Say the cost price of 23 books is $23 so $1 for a book.   The cost of 30 books would be $30, and the selling price of 30 books would be 23$, hence the loss = ($30 - $23)/$30 = ~23.3%.   Answer: 23 1/3 loss %.
<result>C</result>
If C.P. of 23 books is equal to S.P of 30 books , then your gain or loss is ?