If the diameter of the dart board is 36 centimeters, what is the approximate circumference?

C = 2 (pi) r, where c is circumference, and r is radius.

The radius of a circle is half it's diameter. So, r = 36 cm / 2 = 18cm. r = 18cm.

Now, substitute the values in to the formula. c = 2 (3.14) (18 cm) = 113.04 cm.