A shopkeeper bought 120 quintals of wheat. 20% of it was sold at 25% loss. At what percent gain should he sell the rest to gain 25% on the whole transaction?

Step 1: Calculate the amount of wheat sold at a loss

The shopkeeper sold 20% of the 120 quintals of wheat at a loss. So, the amount of wheat sold at a loss is 20/100 * 120 = 24 quintals.

Step 2: Calculate the amount of wheat remaining

The remaining wheat is 120 - 24 = 96 quintals.

Step 3: Calculate the total cost of the wheat

Let's assume the cost price of 1 quintal of wheat is $1. So, the total cost of the wheat is 120 *$1 = $120.

Step 4: Calculate the total selling price for a 25% gain

The shopkeeper wants to gain 25% on the whole transaction. So, the total selling price should be 125/100 * $120 =$150.

Step 5: Calculate the selling price of the wheat sold at a loss

The shopkeeper sold 24 quintals of wheat at a 25% loss. So, the selling price of this wheat is 75/100 * 24 = $18.

Step 6: Calculate the selling price of the remaining wheat

The selling price of the remaining wheat is the total selling price - the selling price of the wheat sold at a loss = $150 -$18 = $132.

Step 7: Calculate the percent gain on the remaining wheat

The cost price of the remaining wheat is 96 * $1 =$96. So, the percent gain on the remaining wheat is (132 - 96) / 96 * 100 = 37.5%.

Therefore, the shopkeeper should sell the rest of the wheat at a 37.5% gain to gain 25% on the whole transaction.