College

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]$\frac{\text{length of } \hat{AB}}{\text{circumference}} = \frac{1}{4}$[/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. 15.7 square units

Answer :

Let's solve the problem step-by-step.

We are given:
- Point [tex]\(O\)[/tex] is the center of the circle.
- Points [tex]\(A\)[/tex] and [tex]\(B\)[/tex] lie on the circle.
- The radius, [tex]\(OA = 5\)[/tex].
- The ratio of the length of arc [tex]\( \hat{AB} \)[/tex] to the circumference of the circle is [tex]\(\frac{1}{4}\)[/tex].

The goal is to find the area of sector [tex]\(AOB\)[/tex].

1. Calculate the circumference of the circle:
[tex]\[
\text{Circumference} = 2\pi \times \text{radius} = 2 \times 3.14 \times 5 = 31.4
\][/tex]

2. Calculate the area of the circle:
[tex]\[
\text{Area of the circle} = \pi \times \text{radius}^2 = 3.14 \times 5^2 = 3.14 \times 25 = 78.5 \text{ square units}
\][/tex]

3. Determine the area of the sector:
Since the length of arc [tex]\( \hat{AB} \)[/tex] is [tex]\(\frac{1}{4}\)[/tex] of the circumference, the sector [tex]\(AOB\)[/tex] will also be [tex]\(\frac{1}{4}\)[/tex] of the area of the circle.
[tex]\[
\text{Area of sector AOB} = \frac{1}{4} \times \text{Area of the circle} = \frac{1}{4} \times 78.5 = 19.625 \text{ square units}
\][/tex]

4. Round to the nearest option:
[tex]\[
19.625 \text{ square units} \approx 19.6 \text{ square units}
\][/tex]

Among the given choices, the closest answer is:
A. 19.6 square units

So, the area of sector [tex]\(AOB\)[/tex] is [tex]\(\boxed{19.6 \text{ square units}}\)[/tex].

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