A farmer harvested 4,500 kg of rice from a 1.5-hectare farm. If the national average yield of rice is 2,500 kg per hectare, by how many kilograms per hectare did the farmer's yield exceed the national average?

The farmer's yield per hectare is $\frac{4{,}500}{1.5} = 3{,}000$ kg/ha. The difference from the national average is $3{,}000 - 2{,}500 = 500$ kg/ha. Option B results from not dividing 4,500 by 1.5 first, option C from subtracting 1,500 from 3,000, and option D is the raw yield per hectare without subtraction.