Closely wrap the thin thread 10 times around the pen.
Mark with ink the begginning and the end of the turns.
Then remove the thread.
Measure the length between the ink marks and call it a¹,repeat for another two times,that is,a²and a³to ensure accuracy of your measurement.
Finally find the average length,a,given by:
a=(a¹+a²+a³)/3
rachaelmusau answered the question on March 6, 2019 at 13:46
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