Question

A custodian carries a large key ring. He measures it and calculates that it has a circumference of 25.12 centimeters. What is the key ring's radius?

Answer 1

By definition of
`\pi`, we have

`\pi=(C)/(d)`

and we deduce

`d = (C)/(\pi)`

Now, recall that the diameter is twice the radius:

`2r=(C)/(\pi)`

and solve for
`r`:

`r=(C)/(2\pi)`

So, divide the circumference by
`2\pi` and you'll find the radius.