You would use this formula for the problem...
(C=2πr) The circumference equals 2 multiplied by pi and radius.
In this problem it says diameter, but the diameter is just twice the length of the radius, so just multiply the radius by 2. Plugin your number.
C=2π(2) since 2 is half of 4, that's your radius.
Your answer is roughly C= 12.57.
You're welcome.
