Question

Jacob made a circle-shaped poster for his geometry class.

If the radius of circle-shaped poster is 9 inches, what is the approximate circumference?

Answer 1

I think it would be 28.26

Answer 2

let us start by identifying the formula for a circumference (perimeter of a circle) \(C = 2 \pi r \)

Answer 3

how would i do that

Answer 4

since the the unit is provided in inches, we want to be consistent and thus our radius becomes \(r = 9 ~in. \)

taking into the consideration of the circumference formula \(C = 2 \pi r \) it follows that our circumference then would be \(C = \pi 2r \rightarrow C= \pi \times 18 ~ in. \) or simply \(C = 18 \pi \)

Answer 5

So the circumference is 18?

Answer 6

no, it IS \(18 \pi \)

Answer 7

inches as the unit

Answer 8

A 56.52 in
B 254.34 in
C 28.26 in
D 113.04 in

Answer 9

that is not even an approximation, but rather a very precise measurement :)
now if you want to use an approximation, you can use \(\pi = 3.14 \)

then it follows that the circumference will be \(C = 18 \pi \rightarrow C= 18~in. \times 3.14 \)

Answer 10

56.52!

Answer 11

but do you understand how it is done now?

Answer 12

yep! thank you!

Answer 13

you begin by identifying the formula for what it is asking for, then plugging in the values