If the cost price of 60 boxes is equal to the selling price of 50 boxes, the gain percent is  Choose the correct choice.
A) 5  B) 10  C) 15  D) 20  E) 25
Let C.P. of each box be Re. 1.   Then, C.P. of 50 boxes = Rs. 50; S.P. of 50 boxes = Rs. 60.   Gain % = 10/50 * 100= 
<gadget id="calculator">10/50 * 100</gadget>
<output>20</output>
20%   Answer:20
<result>D</result>
If the cost price of 60 boxes is equal to the selling price of 50 boxes, the gain percent is