If the diameter of the circle above is 18 in, what is the circumference of the circle?

Formula of circle:

C = 2πr

The radius is half of the diameter, so divide 9 by 2

18/2=9

Then plug in 9 as the radius in the formula.

C = 2π (9)

Using you calculator multiply 2 by the symbol "π" and 9

Exact Form is 18π

Decimal Form is 56.54866776 ...