Area and perimeter: GCSE Maths revision
Perimeter is the distance around. Area is the space inside. Compound shapes: split them into rectangles, triangles and circles you already know.
Formulae
- Rectangle: A = lw
- Triangle: A = ½bh
- Trapezium: A = ½(a + b)h
- Circle: C = πd or 2πr, A = πr²
Try these questions
Cover the answers and have a go first. Worked solutions are underneath.
Area of a rectangle 8 cm by 5 cm
Area of a triangle base 10 cm, height 6 cm
Circumference of a circle radius 7 cm. Leave in terms of π.
Area of a circle diameter 10 cm, to 1 d.p.
Common mistakes
- Using diameter in πr² instead of radius.
- Forgetting units (cm vs cm²).
Answers and working
Frequently asked questions
Is π on the calculator?
Yes. Use the π button unless the question says leave in terms of π or use 3.142.
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