SOLUTION: What is the area of a circle with the circumference 18 pi centimeters??

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Question 145659: What is the area of a circle with the circumference 18 pi centimeters??
Found 2 solutions by edjones, jim_thompson5910:
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
A=pi*r^2
C=pi*d
d=C/pi
d=18pi/pi
d=18 cm
r=18/2=9
pi*9^2=81pi cm^2 area of the circle
.
Ed

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

C=2%2Api%2Ar Start with the circumference of a circle formula



18%2Api=2%2Api%2Ar Plug in C=18%2Api (this is given)


r=%2818%2Api%29%2F%282%2Api%29 Divide both sides by 2%2Api to solve for "r"


r=9 Reduce


So the radius of a circle with a circumference 18 pi centimeters is 9 cm


A=pi%2A%289%29%5E2 Plug in r=9


A=pi%2A%2881%29 Square 9 to get 81



So the area is A=81%2Api which is approximately 254.47 cm