



 
Hi Tracey, The relationship between the circumference $C$ and the diameter $D$ of a circle is \[C = \pi \; D\] where $\pi$ is approximately 3.1516. Thus if you know the diameter of a circle you can find the circumference by multiplying the diameter by $ \pi.$ If you divide both sides of the equation above by $\pi$ it becomes \[D = \frac{C}{\pi}\] and hence if you know the circumference of a circle you can find its diameter by dividing the circumference by $\pi.$ I hope this helps,  


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