# How is $π$ irrational if… [closed]

If we take a rope of length $x$ which is rational quantity and we make a circle out of it, we measure its diameter which is also rational, if we divide a rational number by another rational number we should get a rational number but the division of length of circumference and diameter should give $π$ which is irrational...?

## closed as off-topic by Xander Henderson, vonbrand, José Carlos Santos, Leucippus, Isaac BrowneMay 8 '18 at 0:48

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• When you do that you get an approximate of $\pi$ not the actual value of $\pi$. – The Integrator May 7 '18 at 15:25
• "we measure its diameter which is also rational" : you measure a rationa approximation of the diameter. – Mauro ALLEGRANZA May 7 '18 at 15:25
• If the circumference is rational then the diameter is not. – Michael Hardy May 7 '18 at 15:25
• We know the $\pi$ is irrational because we prove it be so, not because we have measured it. The distinction between mathematics and land surveying was discovered by Ancient Greeks. – Mauro ALLEGRANZA May 7 '18 at 15:27
• Not sure why this is getting downvoted. So you can only ask questions here if you know enough math to not need to ask them, huh? – Jack M May 7 '18 at 16:19

The diameter will not be rational. It will be a rational number divided by $\pi$.