TOPIC
13
Length
454
455
457
Strand: Measures
Strand unit: Length
Estimate, compare, measure and record lengths of a wide variety of objects using
appropriate metric units and selecting suitable instruments of measurement.
Rename units of length in decimal form.
Solve and complete practical tasks and problems involving the addition,
subtraction, multiplication and simple division of units of length (m, cm and km).
Looking back: What the 3rd class programme covered
1. Estimating lengths in metres (m) and centimetres (cm).
2. Renaming units of length in metres (m) and centimetres (cm).
3. Adding and subtracting lengths and relevant problems.
Maths skills used in this topic
1. Applying and problem-solving: Apply mathematical concepts and processes, and plan and
implement solutions to problems, in a variety of contexts.
2. Implementing: Execute standard procedures efficiently with a variety of tools.
Metre stick, ruler, trundle wheel
Vocabulary
Centimetre, metre, kilometre
Teaching points
1. When measuring with a ruler, a common mistake to make is that the children do not begin at
0 on the ruler. Use a glass ruler on an overhead projector or a whiteboard to illustrate how to
measure accurately. Try to source rulers with cm only (no inches or mm) for less able children.
2. Length and width of a table (for instance) – there is no mathematical rule that dictates that the
length is the longer dimension and width the shorter one. By convention, however, we tend to
attribute ‘length’ to the longer and ‘width’ to the shorter dimension. Discuss with the children.
Target board 4:
Which lengths are greater than 0.8? Which lengths are less than a metre?
Change all lengths to centimetres. Compare the lengths in the first row: Which
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is the longest, which is the shortest? Put them in order starting with the largest. Find 2 lengths that
total 1 metre exactly.
Fans:
Show 125cm as metres, i.e. 1.25m. Show various other centimetre lengths as metres.
Show 2m 78cm as centimetres, i.e. 278cm. Show various other metre lengths as centimetres.
Topic suggestions
1. Estimating games are great fun. Divide your class into 2 teams and name something in the
room. Team A has to estimate the length of the item and announce the estimate to the class.
Team B has to say if the item is longer or shorter than the estimate announced by Team A. The
length of the item is then measured. If Team B is right it is awarded a point. Otherwise Team
A is awarded the point. The incentive for Team A is to be as accurate as possible so that it is
more difficult for Team B to judge. For the next round, different item, Team B estimates and
announces and Team A judges whether the item is longer or shorter.
2. Variation on the above: You can have any number of teams. All teams estimate. The team
that’s closest is awarded 3 points, second closest 2 points and third closest 1 point, with a
5-point bonus for any team that estimates exactly.
3. ‘As the crow flies’ is an expression to explain that the distance between 2 places is a straight
line route (no bends on the road or detours around mountains). Discuss this with the children
– how their journey from school would certainly be shorter if they could fly or walk directly.
You could try some measuring experiments between 2 points in the schoolyard. Measure the
direct distance and then set up a circuitous route and measure. Children will learn that the
indirect route may be double (or even more than double) the direct route.
Activity A
Measuring:
1. Nominate some items in the classroom and ask the children to estimate whether the item is
<1m, about 1m or >1m, and then place a counter in the correct box.
2. Choose items appropriate to your classroom environment and the likely experience range
of your students. For example: the length of teacher’s table, metre stick, width of teacher’s
table, length of whiteboard/blackboard, Pat’s height, distance of ceiling from floor, window
ledge, height of chair, length of full sheet of newspaper – tabloid and broadsheet, length of
computer keyboard, length of notice board, width of door, height of bookshelf, length of a
garden tool (such as spade)/golf club/camán, width of corridor.
Differentiation
Lower attainers:
Separate activity page.
Higher attainers:
Create a measuring chart. Divide a page into 5 sections labelled: ‘10cm or less’, ‘11cm to 40cm’,
‘41cm to 70cm’, ‘71cm to 1m’ and greater than 1m. Children investigate the classroom measuring
things and find 5 items for each category.
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Topic
Topic
13
13
1. Use a ruler to measure each of these lines. Estimate before you measure.
Line
A
B
C
D
E
F
1. Will 3 desks that are each 1m 20cm long fit end to end in a room that is 3 12 m long? ___________
G
H
2. A piece of wool measuring 3m 40cm is cut from a ball that has 10m of wool. How much wool is
My Estimate
left? ___________
When I Measured
3. In a high jump competition, Sarah jumped 99cm and Amy jumped 1m 3cm. Who jumped higher
and how much higher did she jump? ___________, ___________
A
F
4. Jimmy is flying a kite. The kite is 73 12 m away from him. If he lets out another 8m of string how far
B
away will the kite be? ___________
D
C
5. Lorraine is fishing and she lets out 10m of line. If she reels in 4m 5cm of line, how much line will
H
E
be out? ___________
G
6. A ruler is 30cm long and you placed 8 rulers end to end. How long would they be in total?
___________
7. A piece of string measuring 9m was cut into 4 equal pieces with none left over. How long was
2. Write as m and cm. Example 4.37m = 4m 37cm
each piece? ___________
(a) 3.83m = ______m ______cm
(b) 4.91m = ______m ______cm
(c) 7.21m = ______m ______cm
(d) 1.59m = ______m ______cm
(e) 2.63m = ______m ______cm
(f) 3.33m = ______m ______cm
(g) 9.95m = ______m ______cm
(h) 8.15m = ______m ______cm
(i) 7.3m
(j) 7.03m = ______m ______cm
= ______m ______cm
8. A building block is 9cm high. How many blocks would I need to make a tower of blocks
1m 44cm high? ___________
9. 4 buses, each 6m 80cm long, are parked end to end. What is their total length? ___________
10. A piece of material measuring 8m 32cm is cut into 8 equal lengths. How long is each piece?
___________
3. Write as m using a decimal point.
4.
(a) 213cm
= ______m
(b) 849cm
= ______m
(c) 447cm
= ______m
(d) 951cm
= ______m
(e) 308cm
= ______m
(f) 380cm
= ______m
(g) 4m 13cm = ______m
(h) 2m 79cm = ______m
(j) 1m 10cm = ______m
(k) 1m 1cm = ______m
(a) m
3.26
(b)
(a) m
9.26
– 2. 13
(c)
+ 2.56
(b)
m
8.35
– 2.16
m
1.17
(d)
+ 3.92
(c)
(d)
– 4.93
Name: _______________________________________
Page 138: Length
(l) 1m
m
4.47
m
6.35
– 2.65
(c) How much farther from Portlaoise is Galway than Wexford? ___________
= ______m
(e)
+ 1.65
m
7.17
(b) Which of the 4 places is farthest from Portlaoise? ___________
(i) 1m 11cm = ______m
m
5.09
m
5.21
– 3.46
Date: ___________________
138
114km
Galway
150km
Dublin
84km
(d) How far would you travel if you went from Wexford to Sligo via (through) Portlaoise? __________
(f)
+ 2.77
(e)
191km
Wexford
m
6.38
+ 2.49
(f)
m
6.08
– 4.49
12. A track measures 400m. How many times must a runner run around the track in order to
run 1km? ___________
© Folens Photocopiables
5.
m
1.25
(a) Which of the 4 places is nearest to Portlaoise? ___________
© Folens Photocopiables
+ 1. 92
Sligo
11. This signpost is in Portlaoise.
13. A bus set out on a journey of 186km. If the driver and passengers stopped for a break after
97 12 km, how far had they left to travel? ___________
14. A swimming pool measures 50m. How many lengths of the pool must a swimmer swim in
order to swim 1km? ___________
Name: _______________________________________
Page 139: Length
Date: ___________________
139
Linkage
Number – Operations: Adding and subtracting lengths
Integration
PE: Athletics (distances/time taken to walk or run a distance)
Maths at home/parental involvement
Lengths at home might be given as a homework task – estimating and/or measuring. How many
stairs would you need to climb to climb 1 metre? What is the longest room in your house?
What is the narrowest room in your house? Are the ceilings in all of the rooms the same height?
How high are they? Find the tallest book in your home. Can you reach the highest shelf? What
things are usually kept on very high shelves? Why? If there is a driveway or garden, how many
cars would fit bumper to bumper? If there are trees near your house are they taller than your
house? If you have a dog, how high is it? How long is it? Who is the tallest person at home?
Who is the tallest person you know?
Notes
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