A fruit-seller buys lemons at 2 for a rupee and sells them at 5 for three rupees What is his gain per cent?

Since, CP of 2 lemon is ₹ 1
∴ CP of 1 lemon is = 1/2 = ₹ 0.5
SP of 5 lemon is ₹ 3.
∴ SP of 1 lemon is = 3/5 = ₹ 0.6
∴ Gain percent = [(0.6 - 0.5)/0.5] x 100
= (0.1/0.5) x 100 = 20%