RANGER Math practice · Geometry · ages 12+
Free circumference and area of a circle practice
Ranger's Math Trail practices the two circle formulas: the circumference (distance around) is 2πr and the area is πr². Each question gives the radius of a round dog pool.
Round your answer to one decimal place. Answers worked with π ≈ 3.14 and answers worked with your calculator's π are both accepted.
Pick a level
Free, no sign-up. The game asks your age once, then every answer comes with a hint and a step-by-step Show me how.
How to do it
- The radius r goes from the center to the edge. The diameter is twice the radius.
- Circumference = 2 × π × r.
- Area = π × r × r.
- Round to one decimal place at the end, not in the middle.
Worked examples
Example 1A round dog pool has a radius of 12 m. What is its circumference (distance around)?
- Circumference = 2πr (2 × π × radius).
- 2 × π × 12 = 24π.
- 24 × 3.14159... ≈ 75.4 m (with 3.14 you get 75.36).
Answer: ≈ 75.4 m
Try one like it →Example 2A round dog pool has a radius of 7 m. What is its area?
- Area of a circle = πr² (π × radius × radius).
- π × 7 × 7 = 49π.
- 49 × 3.14159... ≈ 153.9 m² (with 3.14 you get 153.86).
Answer: ≈ 153.9 m²
Try one like it →Mistakes to watch for
- If you're given the diameter, halve it to get the radius first.
- Area is in square units (m²). Circumference is a length (m).
The game
Questions
Should I use 3.14 or the π button?
Either. The game accepts the answer you'd get with 3.14 and the one you'd get with a calculator's π, both rounded to one decimal place.
What age is it for?
Circles are usually taught in grade 7 (ages 12 to 13).
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