Question

When given a circle with a radius of 4, how do you find the following? explain why.

a. Diameter

b. Circumference

Answer 1

Diameter is 8

Circumference is 8pi ~= 25.13

Explanation:



The diameter is double the radius. So the given radius is 4 and double is 8.

The Circumference is given by C = pi•d or C = 2pi•r

Both of these equations will give the circumference.

C = pi•d

= pi•8

= 8pi ~= 25.13

OR

C = 2pi•r

= 2pi•4

= 8pi ~= 25.13

Answer 2

For finding the diameter, I multiply the radius by 2:

Diameter = 2 × radius

= 2 × 4

= 8

So the diameter is 8. As for the circumference, we can use two ways : either multiply pi times the diameter, or multiply 2 times pi times the radius.

The formulas are

C = πd and C = 2πr

To find the circumference, stick in 8 for d:

C = π × 8

C = 25.13 units