Areas related to circles
Sectors, arcs and rings.
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A sector is a slice of a circle. Its share is angle ÷ 360.
Look: A 90° slice is 90/360 = ¼ of the circle.
✏️ Your turn!
Type your answer and press Check. Kutty will tell you if it is right.
1180° slice: what part of the circle?
260° slice of a 36 cm² circle?
3Arc of 90° on a circle 88 cm round?
! Careful!
✗Using angle ÷ 180.
✓A full turn is 360.
✗Arc length in cm².
✓Arc is a length: cm.
See the whole lesson on one page
A sector is a slice of a circle. Its share is angle ÷ 360.
Slice area = (angle ÷ 360) × whole circle area. Slice edge (arc) = (angle ÷ 360) × whole way round.
Think of it like thisA pizza slice with a 90° corner is a quarter of the pizza, because 90 is a quarter of 360.
Solved together
A clock’s minute hand is 14 cm long. What area does it sweep in 15 minutes? (π = 22/7)
In 15 minutes it turns ¼ of the way: 90°.
Whole circle area.
22/7 × 14 × 14 = 616Take a quarter.
616 ÷ 4 = 154
Answer154 cm².
Now practise it
Kanakku makes new questions on areas related to circles every time. It shows the working and gives a hint when you are stuck.