Math CentralQuandaries & Queries


Question from Jimmy, a teacher:

If I have a straight line with a known length and decide to make a circle out of this know length how would I calculate what the diameter of the circle would be

Hi Jimmy,

For any circle the circumference divided by the diameter is a number we call π. π, pronounced pi is letter in the Greek alphabet. The size of the circle doesn't matter, the quotient is always π, which is approximately 3.1416. Using symbols, if the diameter is D and the circumference is C then C/D = π. Equivalently we can say that C = π × D. Hence if you know the circumference, the length of your line, you can use C = π × D = calculate the diameter,


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