You have been hired to do a broadcast herbicide application on a 10.5‐mile stretch of right‐of-way.

[Steven G]

Here is the question: You have been hired to do a broadcast herbicide application on a 10.5‐mile stretch of right‐of-way. You will be using a boomless nozzle that sprays a 24-foot pattern. At 6 mph and a pressure of 50 psi you have calibrated the sprayer at 36.4 gallons per acre (GPA). Your truck is equipped with a 1,200-gallon tank. The herbicide label recommends 3 quarts of product per acre. How many gallons of herbicide will be needed, and how many total gallons of spray solution will be applied?

I am a bit troubled by some of the wording. Now how many gallons of herbicide will be needed I think means how many gallons of active ingredients I need to use. What troubles me is how many total gallons of spray solution will be applied. Isn't that going to be 1200 gallons???

 

[JeffM]

The amount required is not constrained by the size of the tank. I may only be able to drive 500 miles on a tank of gas, but the size of the tank does not mean that my car must be scrapped after I have driven 500 miles.

Perhaps I do not understand the question.

 

[Dr.Peterson]

I found a video that shows the solution (though I didn't bother watching it all yet to see if it makes sense). The answer turns out to be less than 1200 gallons; I suppose if it had been more, then you'd have to go fill up again. But you aren't required to use it all up.

 

[Otis]

I'm thinking that the herbicide is not added directly to the water tank, but rather to a separate tank. The device mixes a calibrated volume of herbicide in the water spray. That is, the water is a medium which disperses the herbicide over a specific-size swath, as the vehicle moves.

I also googled for information, and I saw a lot of calibration formulas. I think the exercise as posted already contains the necessary information, but it could have been expressed more clearly.

Edit: Grammar typo

 

[Dr.Peterson]

The two places where I found this exact problem show that it is not a mere math problem, but is a sample certification test problem that tests knowledge of the application domain itself {"pesticide safety education"). So one is expected to know what it means. Here is the video.

 

[Steven G]

I found a video that shows the solution (though I didn't bother watching it all yet to see if it makes sense). The answer turns out to be less than 1200 gallons; I suppose if it had been more, then you'd have to go fill up again. But you aren't required to use it all up.

I did find the video. Thanks!