Question

What is the circumference of a circle if I only know the area?

The area is 13dm2

Answer 1

C = 12.75

Circumference is about 12.75 decimeters.

Explanation:

Circumference formula:
`C=2\pi r`

Area formula:
`A=\pi r^2`

You can rearrange the area formula to solve for the radius:

`A=\pi r^2\\r^2=(A)/(\pi) \\r=\sqrt{(A)/(\pi ) }`

Solve for the radius given the area:

`r=\sqrt{(13)/(3.14) }\\r=√(4.14)\\r=2.03`

Use the radius to calculate the circumference:

`C=(2)(3.14)(2.03)\\C=12.75`

Circumference is about 12.75 decimeters.

Answer 2

Answer:12.76

Explanation:

A=π×r^2

13=22/7×r^2

r^2=13÷22/7

r^2=4.14 r=√(4.14) r=2.03

C=2×π×r

C=2×22/7×2.03

C=12.76dm