If you double 4 and if you double 1/2 then add 1, add 8 +1

19?

Step-by-step explanation:

double of 4 is 8, double of 1/2 is 1 and adding them all together is 19

Step-by-step explanation:

Arc length has a formula of

and we have all the info we need to solve for the radius, which we will then use in the circumference formula:

and simplifying a bit,

and a bit more,

. Multiply both sides by 9:

72π = πr . Divide both sides by π to get that

r = 72.

Now we will sub that into the circumference formula to find the circumference. Recall that C = 2πr.

C = 2π(72) so

C = 144π