Circle – Area
A circle’s area is the space it covers, found with A = π × r² using the radius.
This is a free explanation of Circle – Area — a preview, not the full interactive lesson. The lesson, practice, quizzes, and AI Tutor are inside the app.
A circle is a perfectly round flat figure where every point on the edge is the same distance from the center. Use area when a problem involves covering a circular surface — grass seed, paint, or tile. The formula is Area = π × r², and you use π ≈ 3.14 unless told otherwise.
The radius (r) runs from the center to any point on the circle. The diameter (d) crosses the full circle through the center, so d = 2r and r = d ÷ 2. If a problem gives you the diameter, divide by 2 before plugging into the formula. Always square the radius first, then multiply by π.
Two common mistakes: using the diameter where the radius is needed (which doubles your answer), and forgetting to square r — circle area is π × r², not π × r. Apply the exponent before multiplying by π.
Worked example
A circle has radius 7. Find its area. (π ≈ 3.14)
- Write the formula: A = π × r².
- Square the radius first: 7² = 49.
- Multiply by π: A = 3.14 × 49 = 153.86.
153.86 square units
On the test: Area is always measured in square units; if the problem gives a diameter, halve it first.
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