By selling 80 pens, a trader gains the cost of 20 pens. Find his gain percentage?  Choose the most appropriate option:
A) 25%	B) 30%	C) 35%	D) 40%	E) 50%
Let the CP of each pen be Rs. 1.   CP of 80 pens = Rs. 80   Profit = Cost of 20 pens = Rs. 20   Profit% = 20/80 * 100= 
<gadget id="calculator">20/80 * 100</gadget>
<output>25</output>
25%   25%nswer:25%
<result>A</result>
By selling 80 pens, a trader gains the cost of 20 pens. Find his gain percentage?