05-NEM-Gr4-Chap05
7/19/03
7:53 AM
Page 124
CHAPTER 5
1
You will need
Measuring with
Decimetres
• a ruler
• a metre stick
Goal Measure with decimetres and relate
decimetres to centimetres and metres.
Human hair grows about 10 cm each year.
10 cm is also called 1 decimetre, or 1 dm.
• string
• scissors
? How long will your hair be in 5 years,
if you don’t cut it?
A. Look at a metre stick.
How many decimetres are in a metre?
B. Cut a piece of string to a length of 1 dm.
C. Use a 30 cm ruler and your 1 dm string to answer
these questions.
a) How many centimetres are in a decimetre?
b) How many decimetres are in a 30 cm ruler?
decimetre
A unit of length
that is longer
than a centimetre
and shorter than
a metre
1 dm ⫽ 10 cm
10 dm ⫽ 1 m
D. a) How long is your hair in centimetres?
b) Is it possible to measure
the exact length of your
hair in decimetres?
Explain why or why not.
c) What is the length of your
hair to the nearest whole
decimetre?
E. Cut a piece of string to
model the length of
your hair in 5 years.
How long is the string?
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NEL
05-NEM-Gr4-Chap05
7/19/03
7:53 AM
Page 125
Reflecting
1. What does it mean to measure something to the
nearest whole decimetre?
2. a) When might you use decimetres rather
than metres?
b) When might you use decimetres rather
than centimetres?
Checking
3. Find an object of each length in your classroom.
Then measure the object in centimetres.
a) shorter than 1 dm
b) between 1 dm and 2 dm
c) longer than 2 dm
Practising
4. Find an object of each length. Then measure
the object to the nearest whole decimetre.
a) about 3 dm
b) longer than 5 dm
c) between 10 dm and 20 dm
5. Draw a line that is 2 dm long.
a) How long is the line in centimetres?
How do you know?
b) Which number is greater, the decimetre
measurement or the centimetre measurement?
Explain how you could have predicted this.
6. About how many years would it take you to grow
your hair to each length below?
How do you know?
a) 2 m
b) 25 cm
NEL
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