By selling 100 oranges, a vendor gains the selling price of 20 oranges. His gain percent is: 20 25 30 32

The gain percent can be calculated using the formula:

Gain % = (Gain / Cost Price) * 100

Here, the gain is equal to the selling price of 20 oranges.

Let's assume the cost price of 1 orange is $1. Therefore, the cost price of 100 oranges is$100.

The vendor gains the selling price of 20 oranges by selling 100 oranges. So, the selling price of 100 oranges is $100 (cost price) +$20 (gain) = $120.

Therefore, the gain is $20.

Substituting these values into the formula:

Gain % = (20 / 100) * 100 = 20%

So, the vendor's gain percent is 20%.