If the cost price of 12 pens is equal to the selling price of 11 pens, the gain percent is: Choose the correct choice from the following.
A) 80%  B) 90%  C) 9%  D) 40%  E) 10%
Explanation:   Let C.P. of each pen be Re. 1.   Then, C.P. of 11 pens = Rs. 11; S.P. of 11 pens = Rs. 12.   Gain % = 1/11 * 100 = 9%   Answer:9%
<result>C</result>
If the cost price of 12 pens is equal to the selling price of 11 pens, the gain percent is: