If a sprayer is calibrated to deliver 20 gallons per acre, how many acres can be sprayed with a 640-gallon spray tank?

To determine how many acres can be sprayed with a 640-gallon spray tank when the sprayer is calibrated to deliver 20 gallons per acre, you can use the formula:

Number of acres = Total gallons in the tank / Gallons per acre.

In this case, you take the total amount of spray solution in the tank, which is 640 gallons, and divide it by the amount used per acre, which is 20 gallons.

So the calculation would be:

640 gallons / 20 gallons per acre = 32 acres.

This means that with a full 640-gallon spray tank, you can effectively cover 32 acres at the specified rate of application. Therefore, the correct answer is based on accurate arithmetic and understanding of the calibration of sprayers in relation to the size of the tank and the application rate.