Question

The radius of a circle is 6.5. What is the diameter, circumference, and area?

Answer 1

Diameter : `13`
Circumference : `13pi`
Area : `42,25pi`

Explanation:

The diameter is 2 times the radius so the diameter of this circle is 13.

The circumference of a circle of radius `r` is given by the formula `2pir`. So here, the circumference of this circle is `13pi`.

The area of a circle of radius `r` is given by the formula `pir^2`. So here, the area of that circle is `6,5^2pi = 42,25pi`.

Answer 2

See solution below

Explanation:

Diameter:

The diameter is always double the length of the radius.

Assuming d represents diameter:

d = 6.5(2)

d = 13

The diameter of the circle measures 13.

Circumference

The formula for circumference of a circle is dπ, where d is diameter and π is pi.

Now that we know the length of the diameter, we can find the circumference, or distance around the circle.

Assuming that C represents circumference

C = dπ
C = 13π
C = 13π or 40.84

The circumference measures 13π (exact value) or 40.84 (rounded to the nearest hundredth).

Area

The formula for area is A = `r^2`π. The radius measures 6.5, so we have enough information to solve for A

A = `r^2`π
A = `6.5^2`π
A = 42.25π or 132.73

The area is 42.25π `units^2` or 132.73 `units^2`

Hopefully you understand some of the characteristics of circles now!