G
SKILL 38
Find the Perimeter of a Polygon
TEACHING STRATEGY
ALTERNATE INTERVENTION STRATEGY
1. Vocabulary Make sure students understand
the terms perimeter, polygon, regular polygon,
square, trapezoid, parallelogram, pentagon,
and equilateral triangle. To help students with
each type of polygon, have them make a chart
with the name of the figure and its properties.
As examples, for regular polygon, the property
listed is “all identical sides;” for “square,” the
property listed is “4 identical sides;” and so
on. Instruct students to refer to the chart they
have created as they complete the worksheet.
Materials: multiple copies of the game cards below
2. Teach Introduce the idea of perimeter of a
polygon. Ask What must you do first to find
the perimeter of a polygon? [Identify all the
sides of the polygon.] What do you do next?
[Write an equation for the perimeter.] Tell
students that they must substitute the length
of each side into the equation and then find
the sum. Ask Is there an easier way to find
the perimeter of a regular polygon? [Yes, you
can multiply the side length by the number of
sides.]
3. Quick Check Look for these common errors as
students solve the Quick Check exercises.
• Omitting a side length of a polygon thereby
finding an incorrect perimeter.
• Not including units in answers, indicating
confusion about the idea of perimeter.
4. Next Steps Assign the practice exercises
to students who show understanding. For
students who need more support, provide
tutoring using the alternate teaching strategy.
Additional Teaching Resource
Online Transition Guide with Reteach
and Extra Practice worksheets from
previous grade levels
Strategy: Use formulas to find perimeters of
polygons.
8
8
8
P 5 4s
32 units
6
P 5 2(, + w)
28 units
6
P 5 2(, + w)
28 units
P 5 s1 + s2 + s3
21 units
P 5 s1 + s2 + s3 + s4
24 units
8
8
8
7
6
8
8
6
6
4
6
P 5 5s
30 units
1. Distribute decks of game cards to pairs of
students. Tell students they are going to play
Go Fish. Have students shuffle the deck and
deal each student 4 cards. The remaining cards
in their deck are placed face down between
students.
2. The goal of the game is to get the most sets of
three matching cards: one with a figure, one with
the formula for finding its perimeter, and one
with the correct perimeter for that figure.
3. Students take turns asking their partner for a
specific card (a regular pentagon, P 5 5s, 30
units). If the partner has the card, he or she
surrenders it and the original student asks for
another card. If the partner does not have the
card requested, the original student draws a card
from the pile, and the partner asks for a card.
Play continues until all cards have been drawn
and correctly matched.
Transition Guide Course 1
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Name
G
SKILL 38
Date
Find the Perimeter of a Polygon
Example
The perimeter of a polygon is the distance around the
polygon. Figure WXYZ is a trapezoid. Find its perimeter.
W
STEP 1
Identify the sides of the polygon. Trapezoid
WXYZ has 4 sides: WX , XY , YZ , and ZW .
STEP 2
Write an equation for the perimeter.
P 5 WX 1 XY 1 YZ 1 ZW
STEP 3
Substitute the value for the length of each side
into the equation and find the sum.
P 5 4 1 6 1 8 1 6 5 24
4 in.
X
6 in.
Z
6 in.
Y
8 in.
The perimeter of trapezoid WXYZ is 24 inches, or 24 in.
Quick Check
Find the perimeter of each polygon.
1 Figure RST is an
2 Figure EFGH is
equilateral triangle.
3 Figure LMNOP is a
a rectangle.
regular pentagon.
R
L
E
3 ft
H
T
P
M
5m
G
12 ft
Q
S
P5
P5
N
P5
Practice on Your Own
Find the perimeter of each polygon.
4 Figure ABCD is
a square.
A
4 cm
5 Figure RSTU is a
parallelogram.
B
R
trapezoid.
7 ft
S
4 ft
D
C
P5
96
6 Figure JKLM is a
U
P5
J
10 mm
8 mm
T
K
8 mm
M 5 mm L
© Marshall Cavendish International (Singapore) Private Limited.
3 in.
F
P5
Math in Focus®: Singapore Math
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Skill 37
Practice on Your Own
Quick Check
2. |26| 5 6
3. |27| 5 7
Practice on Your Own
4.
6.
8.
10.
12.
14.
|25| 5 5
|8| 5 8
| 6| 5 6
|12| 5 12
|11| 5 11
|0| 5 0
Quick Check
2. 30 ft
3. 25 m
Practice on Your Own
4. 16 cm
5. 22 ft
Quick Check
1. 20.93
Quick Check
1. 10 square inches or 10 in.2
2. 30 square yards or 30 yd2
3. 90 square millimeters or 90 mm2
Practice on Your Own
4. 66 square meters or 66 m2
5. 77 square feet or 77 ft2
6. 164.7 square yards or 164.7 yd2
Skill 40
Quick Check
1. 36 square feet or 36 ft2
2. 100 square meters or 100 m2
3. 144 square centimeters or 144 cm2
Practice on Your Own
625 square centimeters or 625 cm2
90.25 square inches or 90.25 in2
441 square millimeters or 441 mm2
213.16 square feet or 213.16 ft2
Skill 41
Quick Check
1. trapezoid; QT and RS
2. rhombus; BE and CD, BC and ED
3. parallelogram; WZ and XY , WX and ZY
3. 5.045
5. 15.6
8. 6.25
6. 52.32
9. 25
2. 8.2
3. 22.35
Skill 43
Quick Check
Practice on Your Own
4. 0.61
7. 4.57
5. 14.03
8. 0.62
6. 2.88
9. 12.48
2. 38.07
3. 2.595
Skill 44
Quick Check
1. 4.5
Practice on Your Own
4. 14.56
7. 0.084
5. 21.50
8. 32.46
6. 4.14
9. 27.93
2. 2.03
3. 0.17
Skill 45
Quick Check
1. 1.6
Practice on Your Own
4. 3.54
7. 2.5
5. 0.72
8. 2.49
6. 0.127
9. 0.088
2. 43
3. 22
Skill 46
Quick Check
1. 31
Practice on Your Own
4. 7
7. 31
5. 30
8. 18
6. 3
9. 66
2. 25.4
3. 18.9
Skill 47
Quick Check
1. 3.6
132
2. 47.317
Practice on Your Own
1. 28.1
6. 31 mm
Skill 39
4.
5.
6.
7.
Skill 42
4. 16.428
7. 19.018
Skill 38
1. 9 in.
5. trapezoid; SV and TU
6. parallelogram; DG and EF , DE and GF
5.
7.
9.
11.
13.
15.
|1| 5 1
|24| 5 4
|9| 5 9
|29| 5 9
|28| 5 8
|215| 5 15
4. rhombus; GJ and HI , GH and JI
© Marshall Cavendish International (Singapore) Private Limited.
1. |2| 5 2
Math in Focus®: Singapore Math
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