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 :

We are given that:

- The radius of the circle is [tex]$5$[/tex].
- The ratio of the length of arc [tex]$\widehat{AB}$[/tex] to the entire circumference is [tex]$\frac{1}{4}$[/tex].
- We use [tex]$\pi = 3.14$[/tex].

Step 1. Calculate the area of the entire circle.

The area of a circle is given by:

[tex]$$
\text{Area}_{\text{circle}} = \pi r^2
$$[/tex]

Substituting the given values:

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

Step 2. Determine the area of sector [tex]$AOB$[/tex].

Since the sector represents [tex]$\frac{1}{4}$[/tex] of the entire circle, its area is:

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

Rounding [tex]$19.625$[/tex] to a value close to the provided choices, the area of sector [tex]$AOB$[/tex] is approximately [tex]$19.6$[/tex] square units.

Final Answer:

[tex]$\boxed{19.6 \text{ square units}}$[/tex]

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