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ASVAB · Geometry

What is the circumference of a circle with a diameter of 10? (Use π ≈ 3.14)

Reviewed by Jordan Morley, Editorial Lead at 247SimpleTests. Written by the 247SimpleTests Editorial Team from the official source material cited on every question.

Correct answer

31.4

  1. A 78.5
  2. B 314
  3. C 31.4
  4. D 15.7

Why this is the answer

Circumference is π × diameter (C = πd), or equivalently 2πr. With a diameter of 10: C = 3.14 × 10 = 31.4. Be careful not to use the area formula (πr²); the area here would be 3.14 × 5² = 78.5, offered as a distractor. Since the diameter is given directly, C = πd is the fastest route. The circumference is 31.4. Remember that circumference uses the diameter (or 2× radius) to the first power, while area uses the radius squared.
Source: ASVAB MK, Circle Circumference

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About this topic: Geometry

Geometry on the Mathematics Knowledge section covers angles, triangles (including the Pythagorean theorem), circles, polygons, perimeter, area and volume, and basic coordinate geometry such as slope. Formulas are not provided, so they must be memorised. This is one of 19 Mathematics Knowledge questions on geometry, each with a full explanation on a single study page.

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