Page 665 - Basic College Mathematics with Early Integers

642 C HAPTE R 9 I GEOMETRY

PRACTICE 4 Example 4 Find the perimeter of a triangle if the sides are 3 inches, 7 inches,

Find the perimeter of a triangle and 6 inches.
if the sides are 5 centimeters,
9 centimeters, and 7 centimeters
in length. 7 in.
6 in.

3 in.
Solution: The formula for the perimeter is P = a + b + c, where a, b, and c are
the lengths of the sides.Thus,
P = a + b + c
= 3 in. + 7 in. + 6 in.
= 16 in.
The perimeter of the triangle is 16 inches.

Work Practice 4

Recall that to find the perimeter of other polygons, we find the sum of the
lengths of their sides.

PRACTICE 5 Example 5 Find the perimeter of the trapezoid shown below:
Find the perimeter of the 3 cm
trapezoid shown. 3 cm
2 cm
6 km
6 cm
4 km 4 km
Solution: To find the perimeter, we find the sum of the lengths of its sides.
9 km
perimeter = 3 cm + 2 cm + 6 cm + 3 cm = 14 cm
The perimeter is 14 centimeters.

Work Practice 5

PRACTICE 6 Example 6 Finding the Perimeter of a Room
Find the perimeter of the room
shown. Find the perimeter of the room shown below:
9 ft
15 m

10 ft
7 ft
26 m
7 m 15 ft
20 m Solution: To find the perimeter of the room, we first need to find the lengths of
all sides of the room.
This side
This side
must measure must measure
9 feet 10 feet 7 feet 3 feet
15 feet 9 feet 6 feet Copyright 2012 Pearson Education, Inc.

10 feet
7 feet
Answers
4. 21 cm 5. 23 km 6. 92 m 15 feet