1. 18.01 Area & Perimeter of Rectangles

2. A rectangle is a quadrilateral with four right angles
Height (h)
Base (b)
Every rectangle has a base (b) and a height (h).
Perimeter is the distance around the figure.
Area is the number of squares needed to cover the inside of a figure.

3. Perimeter Formula of a Rectangle:
Height (h)
P = 2b + 2h
Base (b)
Area Formula of a Rectangle:
A = b • h
Find the perimeter and area of a rectangle whose base = 4 in. and whose height = 3 in.
P = 2b + 2h
= 2(4 in.) + 2(3 in.)
= 8 in in.
= 14 in.
A = b • h
= 3 in. • 4 in.
= 12 in2

4. A square is a rectangle with 4 equal sides
(b)
Since the b = h = s, the formulas can be changed.
Perimeter Formula of a Square:
P = 4 • s
Area Formula of a Square:
A = s2
Find the perimeter and area of a square whose side = 9 cm.
P = 4 • s
= 4 • 9 cm
= 36 cm
A = s2
= (9 cm)2
= 81 cm2

5. Height (h)
Base (b)
To find a missing side given its area, replace the variables in the formula with their numbers and solve.
Find the missing side.
b = 6 m and A = 54 m2
A = b • h
54 m2 = 6 m • h
9 m = h

6. To find the area or perimeter of a rectangle given one side and a diagonal, use the Pythagorean Theorem to find missing side.
a2 + b2 = c2
(x)2 + (4)2 = (5)2
5 m
x m
x = 25
x2 = 9
4 m
x = 3
P = 2b + 2h
= 2( 4 m) + 2(3 m)
= 8 m + 6 m
= 14 m
A = b • h
= 4 m • 3 m
= 12 m2