Circumference Math Example 2

Follow the full solution, then compare it with the other examples linked below.

Example 2

medium
A circular track has a circumference of 400400 m. Find the radius of the track to the nearest metre.

Solution

  1. 1
    Start with C=2ฯ€rC = 2\pi r and solve for rr: r=C2ฯ€r = \frac{C}{2\pi}.
  2. 2
    Substitute: r=4002ฯ€=200ฯ€โ‰ˆ63.66r = \frac{400}{2\pi} = \frac{200}{\pi} \approx 63.66 m.
  3. 3
    Rounded to the nearest metre: rโ‰ˆ64r \approx 64 m.

Answer

rโ‰ˆ64ย mr \approx 64 \text{ m}
Rearranging the circumference formula to find the radius is a practical skill. This arises whenever you know the perimeter of a circular object and need its radius or diameter.

About Circumference

The total distance around the outside of a circle; equal to ฯ€\pi times the diameter or 2ฯ€r2\pi r.

Learn more about Circumference โ†’

More Circumference Examples

Example 1 easy

Find the circumference of a circle with radius [formula] cm. Leave your answer in terms of [formula]

Example 3 easy

Find the circumference of a circle with diameter [formula] cm. Leave your answer in terms of [formul

Example 4 medium

A bicycle wheel has diameter [formula] cm. How far does it travel in [formula] complete rotations? U

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