Area

Areas of triangles, parallelograms, rhombuses and trapeziums, missing lengths, and areas of shapes made by joining or cutting these.

Key ideas

• The height must be perpendicular to the base it is paired with.
• A parallelogram can be cut and moved into a rectangle with the same base and height.
• A trapezium’s area uses the average of its two parallel sides.
• For a composite shape, split it into simple shapes and add, or take the cut-out parts away.
• To find a missing length, put the area and the known lengths into the formula and solve.

Remember

Watch out

• Using a slanting side as the height.
• Forgetting the ½ for a triangle, rhombus or trapezium.
• Converting square units by 100 instead of 10 000 (m² to cm²).

Worked example