SOLUTION: if the area of a circle is 121 pi then what is the circumference

Algebra ->  Circles -> SOLUTION: if the area of a circle is 121 pi then what is the circumference       Log On


   

Question 1151028: if the area of a circle is 121 pi then what is the circumference
Found 2 solutions by Alan3354, ikleyn:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
if the area of a circle is 121 pi then what is the circumference
----------
Area+=+pi%2Ar%5E2
---------
C+=+2pi%2Ar

Answer by ikleyn(52781) About Me  (Show Source):
You can put this solution on YOUR website!
.

First, you need to find the radius of the circle.


You write for the area

    pi%2Ar%5E2 = 121pi.


Then you cancel pi in both sides

    r%5E2 = 121.


Then you take the square root from both sides

    r = sqrt%28121%29 = sqrt%2811%5E2%29 = 11.


Thus you found the radius of the circle  r = 11.


Then the circumference is

    C = 2%2Api%2Ar = 2%2Api%2A11 = 22pi = 22*3.14 = 69.08 (approximately).     ANSWER