You are making a rectangle from two horizontal rods and two vertical rods. Horizontal rods cost $3 per foot and vertical rods cost $5 per foot. If your budget is $180, then what area is the largest possible area of the rectangle?

Question

Not sure how to start it off..please help

Answer 1

let the length of the horizontal be x ft
let the length of the vertical be y ft

restraint: 3x + 5y =180
y = (180 - 3x)/5 = 36 -(3/5)x

area = xy = x(36 - (3/5)x) = 36x - (3/5)x^2
d(area)/dx = 36 - (6/5)x
= 0 for a max area

(6/5)x = 36

take over ....