Help? I feel like I might be overthinking this..

Question

One method used to irrigate crops is the center-pivot irrigation system. In this method, sprinklers rotate in a circle to water crops. The challenge for the farmer is to determine where to place the pivot in order to water the desired number of acres. The farmer knows the area but needs to find the radius of the circle necessary to find the area. How can the farmer determine this from the formula for the area of a circle A=πr^2 ? Find the formula the farmer could use to determine the radius necessary to irrigate a given number of acres, A. (Hint: one acre is 43,560 square feet.) What would be the radius necessary for the sprinklers to irrigate an area of 133 acres?

Answer 1

You are looking for the radius of the circle that has an area of 133 acres, using the formula:

 

A= π r²

 

So that r comes out in feet, you need to convert A from acres to ft^2

 

A= 133 acres * 43,560 ft/acre= 5793480 ft^2

 

so, r= sqrt ( A/pi)

 

Just put in for A and pi, and take the square root, and that will be the answer.