Algebra 1

a. The circumference formula is $C=\pi d$. Plugging in the given circumference $100=\pi d$. Then solving for $d$ by dividing by $\pi$ giving the expression $100/\pi$ for $d$. b. The area formula is $A=\pi r^{2}$. Plugging in the radius $A=\pi (15.9^{2})=793.8$