Circumference

The circumference is always a bit more than 3 × diameter: C = πd

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About This Practice

A fixed ratio hides between circumference and diameter: the circumference is always a bit more than 3 times the diameter — that multiplier is pi, π ≈ 3.14. Tap “Roll” to send a marked circle one full turn along a line; the distance covered is the circumference — measure it yourself and meet π.

Tap “Roll”: a circle with a marked point rolls one full turn along a line — the distance covered is its circumference. Measuring shows it's always just over 3 diameters: that's π ≈ 3.14.

MediumEstimated Time: 10mincircumferencepirolling measureC=πd

How to Play

  1. Note the marked point on the circle and where it starts.
  2. Tap “Roll” and watch the circle make one full turn along the line.
  3. When the mark returns to the bottom, the distance rolled is the circumference.
  4. Measure: about how many diameters long is that distance?
  5. Remember the conclusion: C = πd, with π ≈ 3.14.

Learning Objectives

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