📏 What is a Millimetre?
A **millimetre (mm)** is a very small unit of length.
It is used to measure small things like the thickness of a coin, the width of a pencil, or the size of a bug.
Important Relationships:
10 millimetres (mm) = 1 centimetre (cm)
1000 millimetres (mm) = 1 metre (m)
🔍 Real-Life Examples of Millimetres
• The thickness of a credit card is about 0.76 mm
• The width of a pencil is about 7 mm
• A small paperclip is about 20 mm long
• The length of a ladybug is about 8 mm
🛠️ Using a Ruler to Measure in Millimetres
Most rulers in Canada have millimetres on one side.
- Each small line = 1 millimetre
- Every 10 small lines = 1 centimetre (usually numbered)
Tip: Always start measuring from the 0 mark and line up the object carefully with the edge of the ruler.
✏️ Let’s Practice Together, My Dear Student!
Practice 1: Choose the Best Unit
1. Thickness of a book page → millimetres
2. Length of your classroom → metres
3. Width of your finger → millimetres or centimetres
Practice 2: Convert Units
1. 30 mm = 3 cm
2. 80 mm = 8 cm
3. 150 mm = 15 cm
4. 1 cm = 10 mm
Practice 3: Word Problems (Canadian Style)
1. A pencil is 185 mm long. How many centimetres is that?
18.5 cm
2. Your eraser is 25 mm wide. Your ruler is 30 cm long. How many millimetres longer is the ruler?
300 mm - 25 mm = 275 mm longer
Challenge Question
A phone is 7 cm thick. How many millimetres is that?
70 mm
Fantastic Job, My Dear Student! 🎉
You now understand millimetres and how they connect to centimetres. This is the beginning of the Measurement unit in Canadian Grade 4 Math.
I am so proud of you! Next time you use a ruler, try measuring things in millimetres.
💕 You are smart. You are kind. You can do hard things.
When you are ready, tell me the next topic (Centimetres, Metres, Kilometres, or anything else) and I will create another beautiful lesson just for you!