Grade 7, Measurement and geometry
Circumference of circles
Find the circumference of circles from the diameter or the radius, or find the diameter.
Three levels
One skill, rising difficulty
Each sheet carries one level. The three are the same skill at rising difficulty, each named for what it practises.
- Level 1: From the diameter
- Find the circumference of each circle. Use 3.14 for pi.
- Level 2: From the radius
- Find the circumference of each circle. Use 3.14 for pi.
- Level 3: Find the diameter from the circumference
- Use the circumference to find the diameter. Use 3.14 for pi.
Worked example
How the sheet explains it
The helper printed at the top of each sheet: one solved example and the steps a student follows, before the first question. Every number sentence in it is proven by the same checker as the answer key.
Level 1: From the diameter
- The circumference is the distance around the circle.
- Circumference = pi × diameter. With 3.14 for pi: 3.14 × 14 = 43.96 cm.
- Check with 3 instead of 3.14: 3 × 14 = 42, which is close to 43.96.
Level 2: From the radius
- The diameter is twice the radius: 2 × 9 = 18 cm.
- Circumference = pi × diameter. With 3.14 for pi: 3.14 × 18 = 56.52 cm.
- Check with 3 instead of 3.14: 3 × 18 = 54, which is close to 56.52.
Level 3: Find the diameter from the circumference
Circumference = 47.1 cm Diameter = 15 cm
- Circumference = pi × diameter, so 3.14 × diameter = 47.1. Find the diameter that fits.
- Try 10: 3.14 × 10 = 31.4. That is less than 47.1, so the diameter is more than 10.
- Try 5 more: 3.14 × 5 = 15.7, which is half of 31.4.
- Add them: 31.4 + 15.7 = 47.1, so the diameter is 10 + 5 = 15 cm.
Goes with
Reference sheets
One-page helpers a student keeps beside this sheet:
- Circles and volume
- Formulas to remember
Every reference, facts and support sheet is listed in the worksheet catalogue.
In the BC curriculum
Content standards
The British Columbia content standard this skill is written for, by the codes used across this site:
- bc.math.7.c.7
The wording of each standard is on the Province's mathematics curriculum page.
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