Question 20
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The circumference of a circle is 9 m. What is the area, in square meters? Express your answer
in terms of π.
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Answer :

To determine the area of a circle when given its circumference, we need to follow a step-by-step approach. Here's a detailed solution:

1. Identify the given information:
- Circumference ([tex]\(C\)[/tex]) of the circle is 9 meters.

2. Recall the formula for the circumference of a circle:
[tex]\[ C = 2\pi r \][/tex]
where [tex]\(r\)[/tex] is the radius of the circle.

3. Solve for the radius ([tex]\(r\)[/tex]):
[tex]\[ r = \frac{C}{2\pi} \][/tex]
Given that [tex]\(C = 9\)[/tex]:
[tex]\[ r = \frac{9}{2\pi} \][/tex]

4. Recall the formula for the area ([tex]\(A\)[/tex]) of a circle:
[tex]\[ A = \pi r^2 \][/tex]

5. Substitute the value of [tex]\(r\)[/tex] into the area formula:
[tex]\[ A = \pi \left(\frac{9}{2\pi}\right)^2 \][/tex]

6. Simplify the expression:
[tex]\[ A = \pi \left(\frac{9^2}{(2\pi)^2}\right) = \pi \left(\frac{81}{4\pi^2}\right) \][/tex]

7. Simplify further:
[tex]\[ A = \pi \cdot \frac{81}{4\pi^2} = \frac{81\pi}{4\pi^2} \][/tex]

8. Cancel out [tex]\(\pi\)[/tex] in the numerator and the denominator:
[tex]\[ A = \frac{81}{4\pi} \][/tex]

So, the area ([tex]\(A\)[/tex]) of the circle expressed in terms of [tex]\(\pi\)[/tex] is:
[tex]\[ \boxed{\frac{81}{4\pi}} \][/tex]

Thus, the area of the circle is [tex]\(\frac{81}{4\pi}\)[/tex] square meters.