Which of the following represents the correct application rate formula to determine tractor speed for a given application rate?

Which of the following represents the correct application rate formula to determine tractor speed for a given application rate?

• A. mph = (gpm x 5,940) / (gpa x w)
• B. mph = gpa x w / (gpm x 5,940)
• C. mph = gpm / (gpa x w x 5,940)
• D. mph = (gpa x w) / (gpm x 5,940)

Answer: (A)

The main idea being tested is how to convert a spray’s flow rate, the target application rate, and the spray width into the tractor’s travel speed in mph. The correct relationship uses the flow rate (gallons per minute) in the numerator and the product of the application rate (gallons per acre) and the spray width (in inches) in the denominator, with a conversion factor that turns those units into miles per hour. The constant 5,940 comes from combining the unit conversions needed (minutes to hours and inches and acres to compatible length/area units) so the result is in mph. This arrangement makes intuitive sense: increasing the flow rate lets you go faster while keeping the same application per area, and increasing the application rate or widening the spray swath requires slowing down to maintain the same per-acre rate. If the width were placed in the numerator or the conversion factor were misapplied, the units wouldn’t cancel to mph and the speed would be incorrect.

The main idea being tested is how to convert a spray’s flow rate, the target application rate, and the spray width into the tractor’s travel speed in mph. The correct relationship uses the flow rate (gallons per minute) in the numerator and the product of the application rate (gallons per acre) and the spray width (in inches) in the denominator, with a conversion factor that turns those units into miles per hour. The constant 5,940 comes from combining the unit conversions needed (minutes to hours and inches and acres to compatible length/area units) so the result is in mph.

This arrangement makes intuitive sense: increasing the flow rate lets you go faster while keeping the same application per area, and increasing the application rate or widening the spray swath requires slowing down to maintain the same per-acre rate. If the width were placed in the numerator or the conversion factor were misapplied, the units wouldn’t cancel to mph and the speed would be incorrect.