Question

The selling price of 12 pens is equal to the cost price of 15 pens. Find the gain per cent.

Answer 1

Let the cost price of the pen be Re 1.
Cost price of 12 pens = Rs 12
SP of 12 pens = CP of 15 pens = Rs 15
Gain = SP - CP = Rs (15 - 12) = Rs 3
Gain% = $\frac{\text{Gain}}{\text{CP}}\times 100\%$
=$\frac{3}{12}\times 100\%=25\%$
Gain% = 25%