Calculating Circumference and Area

Pre-Algebra · Axiom Academy

EXAMPLE Calculating Circumference and Area Find the circumference and area of a circle, and choose the most convenient value of π. A circle has radius . Find its circumference and its area . Nice work! You found both the circumference and the area of the circle. Here's what to carry forward: Two formulas: circumference is ; area is . Pick the right one for what you're measuring. Choose π wisely: use when the radius is a multiple of 7 (like 7, 14, 21) so the 7 cancels; otherwise is usually easier. Exact vs. approximate: leaving an answer as is exact; using or 3.14 gives an approximation like . Units matter: circumference is a length (cm); area is a square measure (cm²). Cancel before you multiply: with and r = 7 , the 7s cancel and the arithmetic stays simple. Both forms have their place: a real-world answer like is fine, while an exact answer like avoids any rounding error.

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