Recently, it was proposed to obtain the equation for the rate of change of the diameter per spin of Toilet paper, here is my proposal:
If we know the thickness of paper and the initial diameter, this decreases 2 times the thickness per spin. The pic shows how to calculate the diameter initial and then for each spin, about 71 spins are enough to finish the paper. For equation 1, the volume of the unwound paper is equal to the volume of the cylinder and is simplified for the diameter.
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