A person purchased 10 dozen pens at the rate of Rs. 4 per dozen. On checking, he found that 20 pens were not working. In order to earn 25% profit, he should sell the remaining pens each at -

Explanation:-

Total C.P. of (10 × 12) i.e.,
120 pens = Rs. (4 × 10) = Rs. 40
Number of working pens
= (120 - 20) = 100
Total selling price of 100 pens $$\eqalign{ & = {\text{Rs}}{\text{.}}\left( {\frac{{125}}{{100}} \times 40} \right) \cr & = {\text{Rs}}{\text{. }}50. \cr & \therefore {\text{S}}{\text{.P}}{\text{.of each pen}} \cr & = {\text{Rs}}.\left( {\frac{{50}}{{100}}} \right) \cr & = {\text{50 paise}}{\text{.}} \cr}$$