Find the area of a 7 cm by 4 cm rectangle.
- Multiply 7 × 4.
- The area is 28 cm², not 28 cm.
Area, units & dimensions
Build a reliable foundation in two-dimensional area.
Area measures a surface
Calculate and compare areas using perpendicular measurements and squared units.
Area counts square units. For a rectangle A = length × width; for a triangle A = base × perpendicular height ÷ 2. The height meets the base at 90°, even if it lies outside the triangle.
Explore the dimensions
Predict first, then change one dimension. Diagrams are schematic; results use the entered values. Rounded values are marked ≈.
Match the units first
Convert lengths to a common unit before multiplying. 1 m² = 10,000 cm² because both dimensions change by a factor of 100.
Circles and approximations
The area of a circle is πr², with radius half the diameter. Keep π or calculator precision until the final rounding step.
Worked examples
A triangle has base 10 m and perpendicular height 6 m.
- A = 10 × 6 ÷ 2.
- The area is 30 m².
Guided Practice
A circular base has radius 3 cm. What is its area?
A first hint
Square the radius before multiplying by π.
Compare your reasoning
A = π(3²) = 9π cm², approximately 28.27 cm².
Practice
Fresh questions · useful feedback
Build fluency, one decision at a time.
Work through eight questions. Two independent correct answers introduce a harder version; supported answers bring the next question back to the foundation. You can use hints at any time.
0 of 8 questions completed
This round saves on this device. It is practice, not a school mark.
Connections
How does the area change if both dimensions of a rectangle are doubled?
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