🧱 See It
Recall place value's rule: moving one column left multiplies by 10, moving one column right divides by 10. Metric length units — millimetres, centimetres, metres, kilometres — work the exact same way. They're just place-value columns with names attached.
✏️ Draw It
| From | To | Operation |
|---|---|---|
| mm | cm | ÷ 10 |
| cm | mm | × 10 |
| cm | m | ÷ 100 |
| m | cm | × 100 |
| m | km | ÷ 1000 |
| km | m | × 1000 |
A "conversion ladder" — climbing up to a bigger unit divides, climbing down to a smaller unit multiplies.
🔢 Write It
To convert to a smaller unit, multiply. To convert to a larger unit, divide.
1000 mm = 1 m
Ask "am I converting to a bigger or smaller unit?" BEFORE choosing to multiply or divide — never guess the operation from the numbers alone.
💡 Worked Examples
Example 1 — Convert 3.5 m to cm.
- Metres are larger than centimetres — converting to a smaller unit, so multiply.
3.5 × 100 = 350- Answer: 350 cm
Example 2 — Convert 2500 mm to m.
- Millimetres are smaller than metres — converting to a larger unit, so divide.
2500 ÷ 1000 = 2.5- Answer: 2.5 m
🧠 Quick Reference
| Unit | Equal to |
|---|---|
| 1 mm | 0.001 m |
| 1 cm | 0.01 m |
| 1 m | 1 m |
| 1 km | 1000 m |
Converting to a SMALLER unit: multiply. Converting to a LARGER unit: divide. Exactly like place value's ×10/÷10 rule, just with measurement names attached.