parimeter of a rectangle

Question

The perimeter of a rectangle is twice the length plus twice the width. The area of a rectangle is the product of its length and width. Suppose we let l represent the length and w represent the width of a rectangle.
a) Write an algebraic expression that represents the perimeter.
b) Write an algebraic expression that represents the area.
c) Calculate the perimeter of a rectangle 12 inches long and 20 inches wide.
d) Calculate the area of the rectangle described in Part C.

Answer 1

L = 2W

a). 

P (peremeter) = 2(L + W)

P = 2(2W + W)

P = 2(3W)

P = 6W

b).

A (area) = LW

A = 2W(W)

A = 2W^2

c).  L = 20 inches, W = 12 inches

P = 2(L + W)

P = 2(20 + 12)

P = 2(32) = 64 inches

d).  L = 20 inches, W = 12 inches

A = LW

A = 20*12 = 240 sq inches