A sprayer is applying 12 gallons per acre at 15 mph. At what speed would it apply 30 gallons per acre?

• A. 3
• B. 6
• C. 9
• D. 12

Answer: (B)

With a sprayer that has a fixed flow, the amount applied per acre is inversely related to ground speed. Slowing down increases the volume applied per acre, while speeding up reduces it.

From 12 gallons per acre at 15 mph, you want 30 gallons per acre, which is 2.5 times more per acre. Since the rate per acre is inversely proportional to speed, the speed must be reduced by the same factor: v2 = v1 × (R1/R2) = 15 × (12/30) = 6 mph.

So, the sprayer would apply 30 gallons per acre at 6 mph. For context, at 9 mph you'd get about 20 gal/acre, and at 3 mph you'd get about 60 gal/acre, illustrating how speed controls per-acre application.