Hello!
The formula for circumference is [tex] 2\pi r[/tex] and the formula for area of a circle is [tex] \pi r^{2} [/tex]. Armed with these formulas, we can begin to find the circumferences and areas of the circles.
20.
C = [tex]2 \pi r [/tex]
C = [tex]2 \pi (6.5)[/tex]
C = [tex]13 \pi [/tex]
C = 13(3.14)
C = 40.8
A = [tex] \pi r^{2} [/tex]
A = [tex] \pi (6.5)^{2} [/tex]
A = [tex] \pi (42.25)[/tex]
A = 132.7
The circumference of the circle is 40.8 in and the area of the circle is 132.7 in².
21.
[Since we are given the diameter for this problem, to find the circumference, we no longer need to multiply the radius by 2 as in [tex]2 \pi r[/tex] because the diameter is the radius × 2. For [tex] \pi r^{2} [/tex] we do need to divide the diameter by 2.]
C = [tex]15.7 \pi [/tex]
C = 49.3
A = [tex] \pi r^{2} [/tex]
A = [tex] \pi (7.85)^{2} [/tex]
A = [tex]61.62 \pi [/tex]
A = 193.5
The circumference of the circle is 49.3 in and the area of the circle is 193.5 in².
And that is all there is to it. I hope this helps you! (:
