The C.P of 10 pens is equal to the S.P of 12 pens. Find his gain % or loss%?  Choose the correct answer.
A) 6 2/5% B) 6 2/7% C) 6 2/3% D) 6 5/3% E) 6 7/3%
10 6 2/3%P = 12 SP   12 --- 2 6 2/3%P loss   100 --- ?   =&gt; 16 2/3%   Answer: 6 2/3%
<result>C</result>
The C.P of 10 pens is equal to the S.P of 12 pens. Find his gain % or loss%?