10.1. Area and Perimeter of Rectangles http://www.ck12.org
Guidance
To find thearea of a rectanglecalculate the product of its base (width) and height (length)A=bh. Theperimeter
of a rectangleisP= 2 b+ 2 h, wherebis the base (or width) andhis the height (or length). If a rectangle is a
square, with sides of lengths, the formula forperimeterisPsquare= 2 s+ 2 s= 4 sand the formula forareais
Asquare=s·s=s^2.
Example A
Find the area and perimeter of a rectangle with sides 4 cm by 9 cm.
The perimeter is 4+ 9 + 4 + 9 = 26 cm. The area isA= 9 · 4 = 36 cm^2.
Example B
The area of a square is 75in^2. Find the perimeter.
To find the perimeter, we need to find the length of the sides.
A=s^2 = 75 in^2
s=√
75 = 5
√
3 in
From this,P= 4(
5
√
3
)
= 20
√
3 in.Example C
Find the area and perimeter of a rectangle with sides 13 m and 12 m.
The perimeter is 2( 13 )+ 2 ( 12 ) = 50 m. The area is 13( 12 ) = 156 m^2.
Watch this video for help with the Examples above.
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/52487CK-12 Foundation: Chapter10AreaandPerimeterofRectanglesB