GeometryFormula

Circle Practice Problems

15 circle problems with full worked solutions, graded from warm-up to stretch — plus an unlimited supply you can generate yourself. Every answer is computed by the same verified function that powers the circle explorer, so the solutions cannot disagree with the formulas. Free, no account, nothing to install.

Formulas you need

  • Area: A=πr2A = \pi r^2
  • Circumference: C=2πrC = 2\pi r
  • Diameter: d=2rd = 2r

where r = radius, d = diameter (d = 2r), A = area, C = circumference, π ≈ 3.14159

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Pick a difficulty, work it out, then check your answer. Every press gives a new question — the numbers are drawn fresh each time, so you can keep going.

Warm-up

  1. A circle has radius r = 5. Find the area (A).

    Answer & working

    78.54 units²

    A = πr² = π · 5² = 25π ≈ 78.54

  2. A circle has radius r = 2. Find the circumference (C).

    Answer & working

    12.57 units

    C = 2πr = 2 · π · 2 = 4π ≈ 12.57

  3. A circle has radius r = 5. Find the diameter (d).

    Answer & working

    10 units

    d = 2r = 2 · 5 = 10

  4. A circle has radius r = 3. Find the area (A).

    Answer & working

    28.27 units²

    A = πr² = π · 3² = 9π ≈ 28.27

  5. A circle has radius r = 5. Find the circumference (C).

    Answer & working

    31.42 units

    C = 2πr = 2 · π · 5 = 10π ≈ 31.42

Core practice

  1. A circle has radius r = 8. Find the area (A).

    Answer & working

    201.06 units²

    A = πr² = π · 8² = 64π ≈ 201.06

  2. A circle has radius r = 9. Find the circumference (C).

    Answer & working

    56.55 units

    C = 2πr = 2 · π · 9 = 18π ≈ 56.55

  3. A circle has radius r = 10. Find the diameter (d).

    Answer & working

    20 units

    d = 2r = 2 · 10 = 20

  4. A circle has radius r = 6. Find the area (A).

    Answer & working

    113.1 units²

    A = πr² = π · 6² = 36π ≈ 113.1

  5. A circle has radius r = 8. Find the circumference (C).

    Answer & working

    50.27 units

    C = 2πr = 2 · π · 8 = 16π ≈ 50.27

Stretch

  1. A circle has radius r = 5.5. Find the area (A).

    Answer & working

    95.03 units²

    A = πr² = π · 5.5² = 30.25π ≈ 95.03

  2. A circle has radius r = 2.5. Find the circumference (C).

    Answer & working

    15.71 units

    C = 2πr = 2 · π · 2.5 = 5π ≈ 15.71

  3. A circle has radius r = 3.5. Find the diameter (d).

    Answer & working

    7 units

    d = 2r = 2 · 3.5 = 7

  4. A circle has radius r = 9.5. Find the area (A).

    Answer & working

    283.53 units²

    A = πr² = π · 9.5² = 90.25π ≈ 283.53

  5. A circle has radius r = 7.5. Find the circumference (C).

    Answer & working

    47.12 units

    C = 2πr = 2 · π · 7.5 = 15π ≈ 47.12

Answers are recomputed from the verified circle function every time this page is built, and every printed line is checked to evaluate correctly. Content last reviewed August 2026. Found a mistake? Tell us — we correct and republish.

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