Question

Please help and explain questions 20-22

Answer 1

Hello!

The formula for circumference is
`2\pi r` and the formula for area of a circle is
`\pi r^(2)`. Armed with these formulas, we can begin to find the circumferences and areas of the circles.

20.
C =
`2 \pi r`
C =
`2 \pi (6.5)`
C =
`13 \pi`
C = 13(3.14)
C = 40.8

A =
`\pi r^(2)`
A =
`\pi (6.5)^(2)`
A =
`\pi (42.25)`
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
`2 \pi r` because the diameter is the radius × 2. For
`\pi r^(2)` we do need to divide the diameter by 2.]

C =
`15.7 \pi`
C = 49.3

A =
`\pi r^(2)`
A =
`\pi (7.85)^(2)`
A =
`61.62 \pi`
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! (: