The answer is C: Divide the arc's degree measure by 360°, then multiply by the circumference of the circle.
Explanation.
Let r = radius of the circle
Then the circumference is C = 2πr.
Let the degree measure of the arc be x degrees.
In radians, the angle is (x/180)π radians
The measure of the arc is
r*(x/180)π = (x/180)*πr
= (2x/360)*πr
= (x360)*2πr
= (x/360)*C
This proves the statement for the answer because
x/360 is the degree measure divided by 360,
C is the circumference.
