Asked by Daryl
Ann wants to build an enclosed area behind her house. One wall of the enclosed area will be the back of the house. She needs the total to be 120 sq feet. She wants to minimize the cost of fence materials. For the sides (W) fence materials cost $3/ft, for the length (L) they cost $5/ft. What dimensions should her fence be?
Answers
Answered by
Damon
c = 2*w*3 + 5 L = 6 w + 5 L
L = 120/w
so
c = 6 w + 600/w
dc/dw = 6 - 600/w^2 = 0 for min or max
w^2 = 100
w = 10
L = 12
L = 120/w
so
c = 6 w + 600/w
dc/dw = 6 - 600/w^2 = 0 for min or max
w^2 = 100
w = 10
L = 12