Bello buys an old bicycle for ₦9,200.00 and spends ₦1,500.00 on its repairs. If he sells the bicycle

Gain percent is always worked out on the total cost, not just the buying price. Bello’s total cost = ₦9,200 (bicycle) + ₦1,500 (repairs) = ₦10,700.

Next find the gain: selling price − total cost = ₦13,400 − ₦10,700 = ₦2,700.

Now use gain % = (gain ÷ total cost) × 100 = (2,700 ÷ 10,700) × 100. Doing the division, 2,700 ÷ 10,700 = 0.25233, and 0.25233 × 100 = 25.23%. So his gain is about 25.23%. If you forget to add the ₦1,500 repair cost you would get 2,700 ÷ 9,200 ≈ 29.3%, which is wrong — money spent on repairs is part of what the item cost him.