Measurement units
Length units and square units are not the same
A length unit measures one direction. A square unit measures a surface in two directions. One square centimetre is a 1 cm by 1 cm square—not simply another way to write one centimetre.
Grades 3–6 · worked example · 3 practice checks
01
Recognize the problem first
- Distance, side length, height, and perimeter use cm, m, or another length unit.
- Area and surface coverage use cm², m², or another square unit.
- Changing from metres to centimetres multiplies length by 100, but changing m² to cm² multiplies area by 10,000.
02
Work through one complete example
Question
A rectangle is 3 m long and 2 m wide. State its perimeter and area with correct units.
- Perimeter is a boundary length: 3 + 2 + 3 + 2 = 10 m.
- Area counts 1 m by 1 m squares: 3 × 2 = 6.
- Write the surface answer as 6 m².
AnswerPerimeter = 10 m; area = 6 m².
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03
Common mistakes to catch
- Writing area as 6 m.
- Writing perimeter as 10 m².
- Using the length conversion factor when converting square units.
0401 02 03
Try three quick checks
What unit should describe the area of a book cover?
Show answer
cm²A square has side 5 m. State its perimeter and area.
Show answer
20 m and 25 m²Convert 2 m² to cm².