MHB What is the formula for finding the area of a circle?

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My Effort:

Circumference = pi•d

10 •pi = pi•d

10•pi/pi = d

10 = d, where d is the diameter of the circle.

Area = pi•r^2, where r is the radius of the circle.

Diameter = 2 times the radius.

10pi = 2r

10pi/2 = r

5pi = r

A = pi•r^2

A = pi(5pi)^2

A = 25•pi^3, which makes no sense.

Only the volume is cubed. This is not a volume question.
 
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mathland said:
Circumference = pi•d
10 •pi = pi•d
10•pi/pi = d
10 = d[/color], where d is the diameter of the circle. Correct![/color]
Area = pi•r^2, where r is the radius of the circle.
Diameter = 2 times the radius.
10pi[/color] = 2r Wrong![/color]
The diameter is 10, not 10pi.
 
Opalg said:
The diameter is 10, not 10pi.

I see my error. Thanks.
 

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