Intermediate Geometry : Plane Geometry

Study concepts, example questions & explanations for Intermediate Geometry

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Example Questions

Example Question #111 : Plane Geometry

A sector in a circle with a radius of \(\displaystyle 16\) has an area of \(\displaystyle 8\pi\). In degrees, what is the measurement of the central angle of the sector?

Possible Answers:

\(\displaystyle 15.50^\circ\)

\(\displaystyle 11.25^\circ\)

\(\displaystyle 10.50^\circ\)

\(\displaystyle 9.75^\circ\)

Correct answer:

\(\displaystyle 11.25^\circ\)

Explanation:

Recall how to find the area of a sector:

\(\displaystyle \text{Area of Sector}=\frac{\text{Measurement of Central Angle}}{360}\times\pi\times r^2\)

Since the question asks for the measurement of the central angle, rearrange the equation like thus:

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times\text{Area of Sector}}{\pi\times r^2}\)

Plug in the given information to find the measurement of the central angle.

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times 8\pi}{\pi\times 16^2}=\frac{2880\pi}{256\pi}=11.25\)

The central angle is \(\displaystyle 11.25\) degrees.

Example Question #112 : Plane Geometry

A sector in a circle with a radius of \(\displaystyle 20\) has a area of \(\displaystyle 50\pi\). In degrees, what is the measurement of the central angle in the sector?

Possible Answers:

\(\displaystyle 39^\circ\)

\(\displaystyle 42^\circ\)

\(\displaystyle 45^\circ\)

\(\displaystyle 36^\circ\)

Correct answer:

\(\displaystyle 45^\circ\)

Explanation:

Recall how to find the area of a sector:

\(\displaystyle \text{Area of Sector}=\frac{\text{Measurement of Central Angle}}{360}\times\pi\times r^2\)

Since the question asks for the measurement of the central angle, rearrange the equation like thus:

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times\text{Area of Sector}}{\pi\times r^2}\)

Plug in the given information to find the measurement of the central angle.

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times 50\pi}{\pi\times 20^2}=\frac{18000\pi}{200\pi}=45\)

The central angle is \(\displaystyle 45\) degrees.

Example Question #113 : Plane Geometry

A sector in a circle with a radius of \(\displaystyle 12\) has an area of \(\displaystyle 48\pi\). In degrees, what is the measurement of the central angle of the sector?

Possible Answers:

\(\displaystyle 110^\circ\)

\(\displaystyle 145^\circ\)

\(\displaystyle 130^\circ\)

\(\displaystyle 120^\circ\)

Correct answer:

\(\displaystyle 120^\circ\)

Explanation:

Recall how to find the area of a sector:

\(\displaystyle \text{Area of Sector}=\frac{\text{Measurement of Central Angle}}{360}\times\pi\times r^2\)

Since the question asks for the measurement of the central angle, rearrange the equation like thus:

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times\text{Area of Sector}}{\pi\times r^2}\)

Plug in the given information to find the measurement of the central angle.

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times 48\pi}{\pi\times 12^2}=\frac{17280\pi}{144\pi}=120\)

The central angle is \(\displaystyle 120\) degrees.

Example Question #114 : Plane Geometry

A sector in a circle with a radius of \(\displaystyle 3\) has an area of \(\displaystyle \frac{1}{2}\pi\). In degrees, what is the measurement of the central angle of the sector?

Possible Answers:

\(\displaystyle 10^\circ\)

\(\displaystyle 40^\circ\)

\(\displaystyle 80^\circ\)

\(\displaystyle 20^\circ\)

Correct answer:

\(\displaystyle 20^\circ\)

Explanation:

Recall how to find the area of a sector:

\(\displaystyle \text{Area of Sector}=\frac{\text{Measurement of Central Angle}}{360}\times\pi\times r^2\)

Since the question asks for the measurement of the central angle, rearrange the equation like thus:

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times\text{Area of Sector}}{\pi\times r^2}\)

Plug in the given information to find the measurement of the central angle.

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times \frac{1}{2}\pi}{\pi\times 3^2}=\frac{180\pi}{9\pi}=20\)

The central angle is \(\displaystyle 20\) degrees.

Example Question #115 : Plane Geometry

A sector in a circle with a radius of \(\displaystyle 12\) has an area of \(\displaystyle 45\pi\). In degrees, what is the measurement of the central angle of the sector?

Possible Answers:

\(\displaystyle 92.5^\circ\)

\(\displaystyle 75.5^\circ\)

\(\displaystyle 112.5^\circ\)

\(\displaystyle 132.5^\circ\)

Correct answer:

\(\displaystyle 112.5^\circ\)

Explanation:

Recall how to find the area of a sector:

\(\displaystyle \text{Area of Sector}=\frac{\text{Measurement of Central Angle}}{360}\times\pi\times r^2\)

Since the question asks for the measurement of the central angle, rearrange the equation like thus:

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times\text{Area of Sector}}{\pi\times r^2}\)

Plug in the given information to find the measurement of the central angle.

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times 45\pi}{\pi\times 12^2}=\frac{16200\pi}{144\pi}=112.5\)

The central angle is \(\displaystyle 112.5\) degrees.

Example Question #116 : Plane Geometry

A sector of a circle with a radius of \(\displaystyle 5\) has an area of \(\displaystyle 3\pi\). In degrees, what is the measurement of the central angle of the sector?

Possible Answers:

\(\displaystyle 43.2^\circ\)

\(\displaystyle 47.2^\circ\)

\(\displaystyle 45.2^\circ\)

\(\displaystyle 49.2^\circ\)

Correct answer:

\(\displaystyle 43.2^\circ\)

Explanation:

Recall how to find the area of a sector:

\(\displaystyle \text{Area of Sector}=\frac{\text{Measurement of Central Angle}}{360}\times\pi\times r^2\)

Since the question asks for the measurement of the central angle, rearrange the equation like thus:

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times\text{Area of Sector}}{\pi\times r^2}\)

Plug in the given information to find the measurement of the central angle.

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times 3\pi}{\pi\times 5^2}=\frac{1080\pi}{25\pi}=43.2\)

The central angle is \(\displaystyle 43.2\) degrees.

Example Question #117 : Plane Geometry

A sector in a circle with a radius of \(\displaystyle 4\) has an area of \(\displaystyle \frac{1}{4}\pi\). In degrees, what is the measurement of the central angle of the sector?

Possible Answers:

\(\displaystyle 5.625^\circ\)

\(\displaystyle 6.225^\circ\)

\(\displaystyle 2.775^\circ\)

\(\displaystyle 8.555^\circ\)

Correct answer:

\(\displaystyle 5.625^\circ\)

Explanation:

Recall how to find the area of a sector:

\(\displaystyle \text{Area of Sector}=\frac{\text{Measurement of Central Angle}}{360}\times\pi\times r^2\)

Since the question asks for the measurement of the central angle, rearrange the equation like thus:

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times\text{Area of Sector}}{\pi\times r^2}\)

Plug in the given information to find the measurement of the central angle.

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times \frac{1}{4}\pi}{\pi\times 4^2}=\frac{90\pi}{16\pi}=5.625\)

The central angle is \(\displaystyle 5.625\) degrees.

Example Question #118 : Plane Geometry

A sector in a circle with a radius of \(\displaystyle 6\) has an area of \(\displaystyle 14\pi\). In degrees, what is the measurement of the central angle of the sector?

Possible Answers:

\(\displaystyle 120^\circ\)

\(\displaystyle 130^\circ\)

\(\displaystyle 150^\circ\)

\(\displaystyle 140^\circ\)

Correct answer:

\(\displaystyle 140^\circ\)

Explanation:

Recall how to find the area of a sector:

\(\displaystyle \text{Area of Sector}=\frac{\text{Measurement of Central Angle}}{360}\times\pi\times r^2\)

Since the question asks for the measurement of the central angle, rearrange the equation like thus:

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times\text{Area of Sector}}{\pi\times r^2}\)

Plug in the given information to find the measurement of the central angle.

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times 14\pi}{\pi\times 6^2}=\frac{5040\pi}{36\pi}=140\)

The central angle is \(\displaystyle 140\) degrees.

Example Question #119 : Plane Geometry

A sector in a circle with a radius of \(\displaystyle 6\) has an area of \(\displaystyle 35\pi\). In degrees, what is the measurement of the central angle of the sector?

Possible Answers:

\(\displaystyle 320^\circ\)

\(\displaystyle 350^\circ\)

\(\displaystyle 330^\circ\)

\(\displaystyle 340^\circ\)

Correct answer:

\(\displaystyle 350^\circ\)

Explanation:

Recall how to find the area of a sector:

\(\displaystyle \text{Area of Sector}=\frac{\text{Measurement of Central Angle}}{360}\times\pi\times r^2\)

Since the question asks for the measurement of the central angle, rearrange the equation like thus:

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times\text{Area of Sector}}{\pi\times r^2}\)

Plug in the given information to find the measurement of the central angle.

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times 35\pi}{\pi\times 6^2}=\frac{12600\pi}{36\pi}=350\)

The central angle is \(\displaystyle 350\) degrees.

Example Question #120 : Plane Geometry

A sector in a circle with a radius of \(\displaystyle 6\) has and area of \(\displaystyle 34\pi\). In degrees, what is the measurement of the central angle of the sector?

Possible Answers:

\(\displaystyle 355^\circ\)

\(\displaystyle 340^\circ\)

\(\displaystyle 350^\circ\)

\(\displaystyle 345^\circ\)

Correct answer:

\(\displaystyle 340^\circ\)

Explanation:

Recall how to find the area of a sector:

\(\displaystyle \text{Area of Sector}=\frac{\text{Measurement of Central Angle}}{360}\times\pi\times r^2\)

Since the question asks for the measurement of the central angle, rearrange the equation like thus:

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times\text{Area of Sector}}{\pi\times r^2}\)

Plug in the given information to find the measurement of the central angle.

\(\displaystyle \text{Measurement of Central Angle}=\frac{360\times 34\pi}{\pi\times 6^2}=\frac{12240\pi}{36\pi}=340\)

The central angle is \(\displaystyle 340\) degrees.

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