# Thread: Stuck on a problem

1. ## Stuck on a problem

Zeta plans to fence off a rectangular field along the bank of a river; no fence is needed along the river. Fencing cost $2 per foot for the ends and$3 per foot for the side parallel to the river. Zeta's budge is $900 1. Let x be the length of the ide of the field that lies along the river. Explain why the formula A(x) = x(225 - .75x) describes the area of the field. I know that the area of a rectangle would be length * width... which would explain where x is coming from but im not sure where the stuff inside the parenthesis are coming from. I think .75 would mean that the width would be 75% of the length but not sure how to get 225. 2. Hi let me draw a pic for you and see if this makes it easier to understand 1000000000001 1000000000001 2y 1000000000001 2y 1000000000001 1111111111111 3x ok now set up a formula for the perimeter$\displaystyle 4y + 3x = 900\displaystyle y = 225 - .75x$Now area is xy so$\displaystyle A= x(225 - .75x)\$