Measuring Length up to 10 m
Primary 1 · Mathematics
Measuring Length up to 10 m
Lesson 3 of 5
13 min
Let's begin
Ishimwe watches men build a fence beside the road in Kigali.
One man pulls a long yellow tape out of a small case.
He calls out a number. Then he plants a pole in the ground.
Today you will learn the unit he is calling out.
The metre is a length that never changes.
Your metre and my metre are exactly the same.
One big step of a grown person is about one metre.
Hold your two arms out wide. That is about one metre too.
A metre ruler and a tape measure both show one metre.
Writing the word metre every time takes long.
So we write just the letter m.
3 m is read: three metres. Say it out loud!
Always write the m after the number. 7 on its own tells us nothing.
Worked example
measure the classroom floor with a 1 m ruler.
Step 1 Put the 0 end of the ruler against the wall.
Step 2 Make a chalk mark where the ruler ends. Say: 1 m.
Step 3 Move the ruler so it starts at your chalk mark.
Step 4 Mark again. Say: 2 m.
Keep going and count each whole metre: 3 m, 4 m, 5 m, 6 m.
The floor is 6 m long.
Careful! On a tape measure, always start at the 0 mark.
Some children hold the 1 mark at the wall instead.
Then they count a metre that is not on the floor.
Their answer comes out one metre too big.
Careful! Never lift the ruler and drop it anywhere. Put it back on your chalk mark.
A tape measure rolls up small and stretches out long.
It is best for long things, like the floor of a room.
A 1 m ruler is best for a desk or a door.
A pencil is not a tool for metres. It is far too short.
Sometimes the last bit of the floor is smaller than the ruler.
Then you say the floor is about 6 m long.
This year you measure things up to 10 m.
Tip
Start at 0. Mark. Move
Say it while you work: start at zero, mark the end, move the ruler.
If you hold the 1 mark at the wall, your answer is one metre too big.
Watch: measuring length in metres.
Do each one, then tap Show answer to check.
Write four metres the short way.
Answer: 4 m. The number first, then the letter m.
Uwase lays a 1 m ruler down 5 times along a wall. How long is the wall?
Answer: 5 m. Each ruler length is one metre.
Which tool is better for the length of the school yard: a pencil or a tape measure?
Answer: a tape measure. A pencil is far too short.
Mugisha holds the 1 mark at the wall, not the 0 mark. Is his answer too big or too small?
Answer: too big. He counted a metre that is not there. Start at 0.
Ask a grown person to take one big step. About how long is that step?
Answer: about 1 m. One big step is close to a metre.
What you learned today
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