SSC CPO SI and ASI 2011 Paper

(2) Let the selling price of 60 articles be Rs. 100.
So, selling price of 15 articles will be $\frac{15}{60}\times 100=25$
Now, Cost price of 60 articles= 100 – 25 = Rs. 75.
Therefore, Gain percent is $\frac{25}{75}\times 100=33\frac{1}{3}\%$