Perimeter and Area Now

Transcription

Perimeter and Area Now
Page 1 of 4
Perimeter and Area
BEFORE
Now
WHY?
You used properties of
rectangles and squares.
You’ll use formulas to find
perimeter and area.
So you can find the area of a
theater’s stage, as in Ex. 22.
3 units
The perimeter of a rectangle is the
sum of the lengths of the sides.
Perimeter is measured in linear units
such as inches (in.), feet (ft),
centimeters (cm), and meters (m).
Word Watch
perimeter, p. 32
area, p. 32
2 units
2 units
3 units
The area of a rectangle is the
number of square units needed to
cover the rectangle. Area is measured
in units such as square inches (in.2),
square feet (ft2), square centimeters
(cm2), and square meters (m2).
Perimeter 3 3 2 2
10 units
Area 6 square units
You can use formulas to find perimeter and area.
Perimeter and Area
Rectangle
Square
width w
side length s
length l
Perimeter P
P 2l 2w
P 4s
Area A
A lw
A s2
EXAMPLE
with
Notetaking
If you forget the formula
for the perimeter of a
rectangle, you could draw
and label a diagram like
the one shown at the top
of this page. Then just add
the lengths of the sides.
1
Finding Perimeter
Find the perimeter of the rectangle or square with the given
dimensions.
a. l 5 feet, w 2 feet
Solution
a. P 2l 2w
Chapter 1
b. P 4s
2(5) 2(2)
4(3)
10 4 14
12
ANSWER The perimeter is 14 ft.
32
b. s 3 centimeters
Number Sense, Patterns, and Algebraic Thinking
ANSWER The perimeter is 12 cm.
Page 2 of 4
Your turn now
Find the perimeter of the rectangle or square.
1.
2.
1 in.
8 cm
7 in.
EXAMPLE
with
Review
Need help with rectangles
and squares? See p. 701.
2
Finding Area
Find the area of the rectangle or square with the given dimensions.
a. l 5 inches, w 3 inches
b. s 10 feet
Solution
b. A s 2
a. A lw
5(3)
102
15
100
ANSWER The area is 15 in.2.
Your turn now
ANSWER The area is 100 ft 2.
Find the area of the rectangle or square.
3.
4.
2m
11 ft
6m
5. Find the perimeter and the area of a rectangle that has a length of
6 inches and a width of 4 inches.
EXAMPLE
3
Using Perimeter and Area
Wheelchair Slalom In a wheelchair slalom
event, athletes weave around cones
and race to the finish line. A diagram of the
rectangular course is shown. Find the
perimeter and the area of the course.
Start
16 m
30 m
Solution
P 2l 2w
A lw
2(30) 2(16)
30(16)
60 32 92
480
Finish
ANSWER The perimeter of the course is 92 m, and the area is 480 m2.
Lesson 1.6
Perimeter and Area
33
Page 3 of 4
INTERNET
Exercises
eWorkbook Plus
CLASSZONE.COM
More Practice, p. 705
Getting Ready to Practice
Vocabulary Copy and complete the statement.
1. The sum of the lengths of the sides of a rectangle is the _?_ of the
rectangle.
2. The number of square units needed to cover a rectangle is the _?_ of the
rectangle.
Find the perimeter and the area of the rectangle or square with the
given dimensions.
3. l 12 inches, w 4 inches
4. l 9 meters, w 7 meters
5. s 7 centimeters
6. s 2 centimeters
7. Art A rectangular painting has a width of 4 feet and a length of 7 feet.
Find the perimeter and the area of the painting.
with
Example
1
2
3
Homework
Exercises
8–17
8–17
18, 20, 22
Online Resources
Practice and Problem Solving
Find the perimeter and the area of the rectangle or square.
8.
3m
15 m
9.
20 in.
CLASSZONE.COM
• More Examples
• eTutorial Plus
Find the perimeter and the area of the rectangle or square with the
given dimensions.
10. l 20 feet, w 2 feet
11. s 4 centimeters
12. s 9 meters
13. l 11 inches, w 6 inches
14. l 15 feet, w 4 feet
15. s 12 centimeters
16. s 13 inches
17. l 8 meters, w 5 meters
18. Gardening You plant a rectangular garden that has a length of 20 feet
and a width of 8 feet. Find the perimeter and the area of the garden.
19. Compare Which has the greater area: a rectangle with a length of 7 feet
j7pe-0106-004-h
and a width of 5 feet, or a square with a side length of 6 feet? Explain
how you know.
20. Basketball A high school basketball court is a rectangle with a length
of 84 feet and a width of 50 feet. What is the perimeter of the court?
34
Chapter 1
Number Sense, Patterns, and Algebraic Thinking
Page 4 of 4
21. Measurement Measure the sides
of the rectangle to the nearest inch.
Use your measurements to find
the perimeter and the area.
History
22. Globe Theatre William Shakespeare’s
plays were performed on the stage of
the old Globe Theatre in London. The
rectangular stage had a length of 43 feet
and a width of 28 feet. Find the area.
Critical Thinking Find the unknown dimension of the rectangle or square.
24. A 8 ft2, l 4 ft, w _?_
23. P 24 in., s _?_
Challenge The figures below can be broken into rectangles and squares.
Find the perimeter and the area of each figure. Explain your method.
25.
26.
5 ft
7m
1 ft
■
Globe Theatre
The old Globe Theatre was
built in 1598, but it no
longer exists. A new Globe
Theatre was opened in
1997. It has a rectangular
stage with a length of
44 feet and a width of
25 feet. What is the area of
the new Globe’s stage?
6m
3 ft
3m 3m 2m
2 ft
Mixed Review
27. You save $3 in September. The next three months you save $6, $12, and
then $24. If this savings pattern continues, how much will you save in
January? (Lesson 1.1)
Solve the equation using mental math. (Lesson 1.5)
28. 4c 32
29. 16 a 11
30. x 18 25
Basic Skills Copy and complete the equation.
31. 6 _?_ 13
32. _?_ 8 19
33. 14 _?_ 2
Test-Taking Practice
INTERNET
State Test Practice
CLASSZONE.COM
34. Multiple Choice What is the area of a rectangular desktop that has a
length of 5 feet and a width of 2 feet?
A. 10 in.2
B. 14 ft
C. 10 ft2
D. 14 ft2
35. Short Response Does a rectangular garden with a length of 6 feet and
a width of 4 feet, or a square garden with side length 5 feet, have the
greater area? Which requires more fencing? Explain.
Lesson 1.6
Perimeter and Area
35