Dimensions of a Rectangle

Question

Find the dimensions of the rectangle of maximum area that can be formed from a 20-in.

piece of wire.

Answer 1

A = L w

20 = 2L + 2w ---> 10 = L + w

----> L = 10 - w

A = (10-w)w

A(w) = (10-w)w , so area is a function of width w

= 10w - w^2

0 = dA/dw = 10 - 2w

10 = 2w

w = 5

Length and width are both 5