05-NelsonMathGr5-Chap05
6/24/04
11:58 AM
Page 138
CHAPTER 5
You will need
Border
size
• newsprint
Width
Length
+ width
2 cm
3 cm
• a calculator
Aaron wants to put a border around
his picture. Then he wants to put
trim around the border.
20 cm
Perimeter
1 cm
Develop and use a rule to calculate the
perimeter of a rectangle.
B. Calculate the sum of the length and width.
Calculate the perimeter. Record your answers.
C. Sketch Aaron’s picture with borders of 2 cm, 3 cm,
and so on. Each time, do the calculations as in
Parts A and B and record the answers in your chart.
Continue until the perimeter is 120 cm.
20 cm
He has 120 cm of trim.
border size
? What is the greatest border
size Aaron can use?
Length
width?
24 cm
Goal
A. What is the length of Aaron’s picture with a 1 cm border?
What is the width? Record your answers in a chart.
• a ruler
length?
5
Measuring the
Perimeter of a
Rectangle
24 cm
1 cm
D. How can you calculate the perimeter of a rectangle if you
know the length and the width? Write your rule in words.
■ cm
Aaron’s Method
E. What is the greatest border size Aaron can use?
Explain your thinking.
Reflecting
Understand the Problem
The trim goes around the border.
1. How did you know when you had the greatest
possible border?
The border with the picture inside forms a rectangle.
The perimeter of the rectangle cannot be greater than
120 cm or there won’t be enough trim.
2. Why does the rule you wrote in Part D make sense?
How would you change the rule to apply it to a square?
Make a Plan
3. Why can’t you use your rule from Part D to calculate
the perimeter of a triangle?
I’ll calculate the perimeter with a 1 cm border.
If the perimeter is less than 120 cm, I’ll try a bigger
border until the perimeter is 120 cm.
Checking
138
Carry Out the Plan
4. How much trim would Aaron need if he used a 5 cm border?
I’ll sketch a 20 cm by 24 cm rectangle on newsprint.
I can draw different-sized borders around it.
5. What is the perimeter of a picture that is 10 cm wide and
15 cm long?
NEL
NEL
139
05-NelsonMathGr5-Chap05
6/24/04
11:58 AM
Page 138
CHAPTER 5
You will need
Border
size
• newsprint
Width
Length
+ width
2 cm
3 cm
• a calculator
Aaron wants to put a border around
his picture. Then he wants to put
trim around the border.
20 cm
Perimeter
1 cm
Develop and use a rule to calculate the
perimeter of a rectangle.
B. Calculate the sum of the length and width.
Calculate the perimeter. Record your answers.
C. Sketch Aaron’s picture with borders of 2 cm, 3 cm,
and so on. Each time, do the calculations as in
Parts A and B and record the answers in your chart.
Continue until the perimeter is 120 cm.
20 cm
He has 120 cm of trim.
border size
? What is the greatest border
size Aaron can use?
Length
width?
24 cm
Goal
A. What is the length of Aaron’s picture with a 1 cm border?
What is the width? Record your answers in a chart.
• a ruler
length?
5
Measuring the
Perimeter of a
Rectangle
24 cm
1 cm
D. How can you calculate the perimeter of a rectangle if you
know the length and the width? Write your rule in words.
■ cm
Aaron’s Method
E. What is the greatest border size Aaron can use?
Explain your thinking.
Reflecting
Understand the Problem
The trim goes around the border.
1. How did you know when you had the greatest
possible border?
The border with the picture inside forms a rectangle.
The perimeter of the rectangle cannot be greater than
120 cm or there won’t be enough trim.
2. Why does the rule you wrote in Part D make sense?
How would you change the rule to apply it to a square?
Make a Plan
3. Why can’t you use your rule from Part D to calculate
the perimeter of a triangle?
I’ll calculate the perimeter with a 1 cm border.
If the perimeter is less than 120 cm, I’ll try a bigger
border until the perimeter is 120 cm.
Checking
138
Carry Out the Plan
4. How much trim would Aaron need if he used a 5 cm border?
I’ll sketch a 20 cm by 24 cm rectangle on newsprint.
I can draw different-sized borders around it.
5. What is the perimeter of a picture that is 10 cm wide and
15 cm long?
NEL
NEL
139
05-NelsonMathGr5-Chap05
6/24/04
11:58 AM
Page 140
Practising
Mental Imagery
6. How much trim would Aaron need if he decided
not to use a border?
24 cm
20 cm
Estimating Distances
Each letter on the number line represents a different distance.
A
7. Calculate the length of fencing needed to go around each
rectangular garden.
a)
b)
4m
B
C
D
E
0 km
1000 km
A. Which letter represents 500 km?
5m
B. Estimate the distance that each other letter represents.
5m
Try These
8m
1. Estimate the number that each letter represents.
a)
A
B
C
D E
8. Juanita used a trundle wheel to measure the length of
a basketball court as 22.5 m and the width as 12.8 m.
What is the perimeter?
0
b)
9. Which rectangle has a greater perimeter?
How much greater is it? How do you know?
A. 4.5 cm by 7.0 cm
B. 3.5 cm by 7.5 cm
10. a) How does the perimeter of this rectangle change
if you add 5 m to the length?
b) How does the perimeter change if you triple the
length and the width of the rectangle?
A
B
C
D
0
c)
5m
E
500
A
B
C
D
0
7m
11. What is the greatest size of border you can use to frame
a 22 cm by 28 cm picture if you have 1.8 m of trim?
E
300
2. Place each number on a number line.
a) 15, 45, 50, 75, 99
12. To calculate the perimeter of a rectangle, Ian doubles
the length and doubles the width and adds the results.
Is his rule correct? Explain.
0
13. a) Draw three different rectangles with sides that are
whole numbers of centimetres.
b) Calculate the perimeter of each rectangle. Are the
perimeters even or odd? Think about your perimeter
rule and explain why.
140
10 000
100
b) 0.2, 0.4, 0.5, 0.75
0
NEL
NEL
1
141