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 } \widehat{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 :

To solve this problem, we need to find the area of a sector of a circle. The circle has a radius of 5 units, and we know that the arc from point A to point B is [tex]\(\frac{1}{4}\)[/tex] of the circle's circumference.

First, let's calculate the area of the whole circle using the formula:

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

Plugging in the values given:

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

Next, the problem states that the arc length of [tex]\( \hat{AB} \)[/tex] constitutes [tex]\(\frac{1}{4}\)[/tex] of the circle's circumference. This tells us that the sector also represents [tex]\(\frac{1}{4}\)[/tex] of the total area of the circle.

So, we find the area of sector [tex]\(AOB\)[/tex] by taking [tex]\(\frac{1}{4}\)[/tex] of the total area of the circle:

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

Among the options provided, we need to choose the closest value to the calculated area:

The closest is:
A. 19.6 square units

Therefore, the area of sector [tex]\(AOB\)[/tex] is approximately 19.6 square units.