If the cost price of 15 pencils is equal to the selling price of 10 pencils, what is the gain or loss percentage?

20% gain 30% loss 50% gain 40% loss

50% gain

Cost price of 15 pencils = Selling price of 10 pencils \(\frac{CP}{SP}\) = \(\frac{10}{15}\)  gain% = (15 - 10) × \(\frac{100}{10}\)  = 50% gain