Circle partsRadius to 12
Name: Date:
Use π = 3.14. Find the area of each slice.
1Area of the slice cm²
2Area of the slice cm²
3Area of the slice cm²
4Area of the slice cm²
5Area of the slice cm²
6Area of the slice cm²
Sector area worksheets
A sector is a slice of a circle, and its area is that same fraction of the whole circle's area. These free printable worksheets keep to the slice alone.
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Sector area
The answer key prints on a separate page.
What's on this sheet
The circle's area is πr², and the slice is that times the angle over 360. Writing the fraction of the turn down first is the habit worth building: 120 over 360 is a third, and a third of the circle is easier to picture — and easier to check — than a formula with two multiplications in it.
Why this sheet works
Every angle here divides 360 exactly and every answer lands on two decimal places, so nothing on the paper says round to the nearest tenth. π is 3.14 throughout, the same as every other circle sheet on the site.
How this one works
One question from this sheet, worked through a step at a time.
Sector: 180° of a circle, radius 9
180/360=1/2
3.14 × 9 × 9=254.34
1/2of254.34=127.17
127.17 cm²
- A slice is a FRACTION of the whole circle, and the angle says which fraction. A full turn is 360°, so 180° is 180 out of 360 — that is 1/2 of the circle. Write that down before touching a formula.
- Now the whole circle, as if there were no slice. Its area is π × r × r — only the r is squared: 3.14 × 9 × 9 = 254.34.
- Then take the slice's share of it: 1/2 of 254.34 is 127.17.
- So the area of the slice is 127.17 cm². Check the unit against what was asked — a curved edge is a length and a slice is an area, and getting cm² where you expected the other one means you answered the other question.