Math CentralQuandaries & Queries


Question from Ally:

A cylinder has a diameter of 3.5 cm. How many times will a thread 143mm go round the cylinder?

Hi Ally,

I think you should have both measurements in the same units so express the diameter in millimeters.

If $C$ is the circumference of a circle and $d$ is its diameter then $C = \pi\;d.$ What is the circumference of your cylinder? How many times will a thread of length 143 mm go around that circumference?


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