High School

Select the correct answer.

Points [tex]A[/tex] and [tex]B[/tex] lie on a circle centered at point [tex]O[/tex]. If [tex]OA = 5[/tex] and [tex]\frac{\text{length of } \hat{B}}{\text{Circumference}} = \frac{1}{4}[/tex], what is the area of sector [tex]AOB[/tex]? Use the value [tex]\pi = 3.14[/tex], and choose the closest answer.

A. 19.6 square units
B. 39.3 square units
C. 7.85 square units
D. 157 square units

Answer :

To solve this question, we need to find the area of the sector [tex]\(AOB\)[/tex] in the circle. We're given the following information:

- The radius [tex]\(OA = 5\)[/tex].
- The fraction of the circumference that corresponds to the arc [tex]\(\widehat{B}\)[/tex] is [tex]\(\frac{1}{4}\)[/tex].
- We also have the value of [tex]\(\pi = 3.14\)[/tex].

### Steps to solve the problem:

1. Calculate the Area of the Entire Circle:

The formula for the area of a circle is:

[tex]\[
\text{Area} = \pi \times \text{radius}^2
\][/tex]

Plugging in the values, the area of the circle is:

[tex]\[
\text{Area} = 3.14 \times 5^2 = 3.14 \times 25 = 78.5 \text{ square units}
\][/tex]

2. Find the Area of the Sector:

We're given that the arc associated with the sector is [tex]\(\frac{1}{4}\)[/tex] of the circle's circumference. The area of a sector is proportional to the arc length of that sector. This means the area of the sector [tex]\(AOB\)[/tex] will also be [tex]\(\frac{1}{4}\)[/tex] of the entire circle's area.

[tex]\[
\text{Sector Area} = \frac{1}{4} \times 78.5 = 19.625 \text{ square units}
\][/tex]

The closest answer from the given options is:

A. 19.6 square units

Therefore, the correct choice is A. 19.6 square units.

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