1.4 Area and Perimeter

Find the area and perimeter of squares, rectangles, and triangles
Find a missing dimension given the area and one dimension

1. Area and Perimeter
Objectives
•Find the area and perimeter of squares, rectangles, and
triangles.
•Find a missing dimension given the area or perimeter and
one dimension

2. area –the number of square units that will completely cover
a shape without overlapping
rectangle area formula –one of the first area formulas you
learned was for a rectangle: A= bh, where bis the
length of the base of the rectangle and his the height
of the rectangle.
square formula–since the base and height of a square are
the same, the formula for the area of a square can
also be written as A= s
2
, where sis the length of the
side.
b
h A =bh

3. The area of a triangle is one-half that of a rectangle with the
same height and base:
triangle formula–1
or
22
bh
AbhA

4. perimeter‒ the distance around an object
For a rectangle, the formula for perimeter is
P= 2b+ 2hor P= 2(b+ h)
For squares, it’s just P= 4s.
Triangles don’t have a formula –just add up the sides.

5. Examples
1.If a rectangle has a base of 10 in. and an area of 110 in
2
,
what is its height?
2.What is the side of a square with area 81 m
2
?
3.If a triangle has a height of 6 cm and an area of 24 cm
2
,
what is the length of its base?

6. Examples
1.If a rectangle has a base of 10 in. and an area of 110 in
2
,
what is its height?
2.What is the side of a square with area 81 m
2
?
3.If a triangle has a height of 6 cm and an area of 24 cm
2
,
what is the length of its base?110
11 in.
10
Abh
A
h
b

 2
81
819 m
s
s

 6
24
2
324
8
b
b
b


