What is the first term of the geometric sequence below?

Geometric sequences use either division or multiplication as its common ratio.  The pattern here is multipication by 5.  Therefore, we would need that first term to be 1/5 because 1/5 * 5 = 1, the next term in the sequence. 1*5 = 5, 5*5 = 25, etc.

Answer = 15 pi or about 37.12

Explanation: First you find the circumference using the formula c=2(pi)r. Radius = 18
C=2pi(18). Circumference= 36pi

Next find the measure of the arc. Multiply (36pi) by (150*degree of the arc*/360*total degree of a circle*). Plug into calculator.