Imagine that you were given a circle with a radius you do not know. You were given that the circumference whas 109.9557428756427633... and she said "What is the radius?", you said 35, she said "How do you know that?" you said divide circumference by \(\varpi \) (3.141592...) and then she leaves.
But, wouldn't that give a diameter of 35, therefore the radius 17.5.....? And a big ol' yeet backatcha.