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

  • MHB
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In summary, the circumference of a circle is equal to pi times the diameter, and the area is equal to pi times the radius squared. The diameter is twice the radius, and in this case, the diameter is equal to 10. Therefore, the radius is 5 and the area is 25 times pi. However, the final calculation for the area, where the radius is cubed, does not make sense as this is not a volume question.
  • #1
mathland
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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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  • #2
mathland said:
Circumference = pi•d
10 •pi = pi•d
10•pi/pi = d
10 = d, where d is the diameter of the circle. Correct!
Area = pi•r^2, where r is the radius of the circle.
Diameter = 2 times the radius.
10pi = 2r Wrong!
The diameter is 10, not 10pi.
 
  • #3
Opalg said:
The diameter is 10, not 10pi.

I see my error. Thanks.
 

1. What is the formula for finding the area of a circle?

The formula for finding the area of a circle is A = πr², where A represents the area and r represents the radius of the circle.

2. How do you calculate the area of a circle?

To calculate the area of a circle, you can use the formula A = πr² or you can use the diameter of the circle (d) and the formula A = (π/4)d².

3. Can you explain the meaning of each part of the formula for finding the area of a circle?

The symbol π represents the mathematical constant pi, which is approximately equal to 3.14. The letter r represents the radius of the circle, which is the distance from the center to any point on the circle's edge. The exponent ² means to multiply the radius by itself, or to square it.

4. How do you find the radius of a circle if you know the area?

To find the radius of a circle if you know the area, you can rearrange the formula A = πr² to solve for r. This would give you the formula r = √(A/π), where r represents the radius and A represents the area.

5. Can the formula for finding the area of a circle be used for any size circle?

Yes, the formula A = πr² can be used for any size circle, as long as you have the correct value for the radius. This formula is a universal rule for finding the area of a circle, regardless of its size.

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