Measuring Length up to 10 m
Primary 1 · Mathematics
Measuring Length up to 10 m
Lesson 2 of 5
12 min
Let's begin
Keza helps her mama lay a new mat in the front room.
Keza opens her hand wide. She walks her hand along the mat and counts.
Her big sister counts the same mat too. They get different numbers!
Today you will find out why.
You do not always have a ruler.
You can measure with your hand-span. Open your hand wide.
The span goes from your thumb to your little finger.
You can measure with your steps. Walk heel to toe along the floor.
You can measure with a stick or a piece of rope.
The thing you measure with is called a unit.
Lay your unit down end to end, like bricks in a wall.
Do not leave a space. A gap makes your number too small.
Do not let them climb on top of each other. An overlap makes your number too big.
Start at one end of the thing. Stop at the other end.
Worked example
Mutesi measures the mat in steps.
Step 1 Put one heel at the edge of the mat.
Step 2 Put the next heel against her own toes. No gap!
Step 3 Count each step out loud: 1, 2, 3, 4, 5, 6.
The mat is 6 of Mutesi's steps long.
Gatete has bigger feet. He walks the same mat in 4 steps.
Keza and her big sister measured the same table.
| Who measured | Unit | How many |
|---|---|---|
| Keza | her hand-span | 12 |
| Her big sister | her hand-span | 8 |
Careful! 12 is more than 8. But the table did not grow.
Keza's hand is smaller. So she needs more hand-spans.
A small unit gives a big number. A big unit gives a small number.
Your hand and my hand are not the same size.
So we need one unit for everybody. That unit is the metre.
Tip
No gaps. No overlaps
Lay each hand-span down like bricks in a wall.
A gap makes your number too small. An overlap makes it too big.
Watch: measuring without a ruler.
Do each one, then tap Show answer to check.
Uwase leaves gaps between her hand-spans. Is her number too big or too small?
Answer: too small. The gaps are not counted.
Mugisha measures a bench in steps. His father measures the same bench. Who counts more steps?
Answer: Mugisha. His feet are smaller, so he needs more steps.
A mat is 8 of Keza's hand-spans. The same mat is 5 of her mama's hand-spans. Whose hand is bigger?
Answer: her mama's hand. A bigger hand needs fewer spans.
Two children measure the same door in hand-spans. Do they always get the same number?
Answer: no. Their hands are different sizes.
Now measure your own table in hand-spans. Count with no gaps.
Answer: your own number. Measure it again to check you get the same.
What you learned today
Quick check
You leave gaps between your hand-spans. Your number is...
