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This topic covers the parts of a circle and calculating circumference (πd) and area (πr²), along with arc length and sector area for parts of a circle. It's a core topic in GCSE and iGCSE Maths with Edexcel and the other major boards. This free interactive course teaches the method with worked examples and gives instant-feedback practice questions to lock it in.
How you do it
Circumference is pi times the diameter and area is pi times the radius squared. The most common slip is using the diameter where the formula needs the radius, so halve it first. For arcs and sectors, take the fraction of the full circle that the angle represents.
Before you start
Everything here rests on area and perimeter. You will lean on this again for arcs, sectors and circle theorems.
What you learn
From these you can find the distance around a circle, the space inside it, and the size of a slice of it. The radius (r) goes from the centre to the edge; the diameter (d = 2r) crosses the whole circle through the centre. A sector is a slice of a circle between two radii, like a slice of pizza. The course works through parts of a circle, circumference and area, arcs and sectors and semicircles and reverse problems. Every section has instant-feedback practice questions matched to Edexcel iGCSE 4MA1 and the other major GCSE boards, and the course finishes with full exam-style questions you mark yourself.
Related Topics
Circles is a Geometry topic in the GCSE syllabus, covered here at Foundation tier. There are 3 teaching sections and 2 fully worked examples, plus 3 sets of check questions. Related topics students usually take next include Loci & Construction, Pythagoras' Theorem, Sine & Cosine Rule and Transformations. You can drill this strand further on the Geometry revision engine, with your accuracy saved to your skill tree.
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