High School Math : High School Math

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #2 : How To Find The Area Of A Sector

In the figure, PQ is the arc of a circle with center O. If the area of the sector is 3\piwhat is the perimeter of sector?

Picture_16

Possible Answers:

3 + 2\pi

12 + \pi

6 + \pi

12 + 2\pi

1 + \pi

Correct answer:

12 + \pi

Explanation:

First, we figure out what fraction of the circle is contained in sector OPQ: \frac{30^{\circ}}{360^{\circ}}= \frac{1}{12}, so the total area of the circle is \dpi{100} \small 12\times 3\pi=36 .

Using the formula for the area of a circle, {\pi}r^{2}, we can see that \dpi{100} \small r=6.

We can use this to solve for the circumference of the circle, 2{\pi}r, or 12{\pi}.

Now, OP and OQ are both equal to r, and PQ is equal to \dpi{100} \small \frac{1}{12} of the circumference of the circle, or {\pi}.

To get the perimeter, we add OP + OQ + PQ, which give us 12+{\pi}.

Example Question #1 : How To Find The Length Of An Arc

If a quarter of the area of a circle is , then what is a quarter of the circumference of the circle?  

Possible Answers:

Correct answer:

Explanation:

If a quarter of the area of a circle is , then the area of the whole circle is .  This means that the radius of the circle is 6.  The diameter is 12.  Thus, the circumference of the circle is .  One fourth of the circumference is .  

Example Question #1 : How To Find The Length Of An Arc

Figure not drawn to scale.

In the figure above, circle C has a radius of 18, and the measure of angle ACB is equal to 100°. What is the perimeter of the red shaded region?

Possible Answers:

36 + 10π

18 + 36π

36 + 20π

36 + 36π

18 + 10π

Correct answer:

36 + 10π

Explanation:

The perimeter of any region is the total distance around its boundaries. The perimeter of the shaded region consists of the two straight line segments, AC and BC, as well as the arc AB. In order to find the perimeter of the whole region, we must add the lengths of AC, BC, and the arc AB.

The lengths of AC and BC are both going to be equal to the length of the radius, which is 18. Thus, the perimeter of AC and BC together is 36.

Lastly, we must find the length of arc AB and add it to 36 to get the whole perimeter of the region.

Angle ACB is a central angle, and it intercepts arc AB. The length of AB is going to equal a certain portion of the circumference. This portion will be equal to the ratio of the measure of angle ACB to the measure of the total degrees in the circle. There are 360 degrees in any circle. The ratio of the angle ACB to 360 degrees will be 100/360 = 5/18. Thus, the length of the arc AB will be 5/18 of the circumference of the circle, which equals 2πr, according to the formula for circumference.

length of arc AB = (5/18)(2πr) = (5/18)(2π(18)) = 10π.

Thus, the length of arc AB is 10π.

The total length of the perimeter is thus 36 + 10π.

The answer is 36 + 10π.

Example Question #2 : How To Find The Length Of An Arc

Find the arc length of a sector that has an angle of 120 degrees and radius of 3.

Possible Answers:

Correct answer:

Explanation:

The equation for the arc length of a sector is .

Substitute the given radius for  and the given angle for  to get the following equation:

Simplify:

Example Question #2 : How To Find The Length Of An Arc

Possible Answers:

Correct answer:

Explanation:

 

Example Question #1 : How To Find The Length Of An Arc

Find the circumference of the following sector:

6

Possible Answers:

Correct answer:

Explanation:

The formula for the circumference of a sector is

,

where  is the radius of the sector and  is the fraction of the sector.

Plugging in our values, we get:

Example Question #1 : How To Find The Length Of An Arc

Circle

In the circle above, the angle A in radians is 

What is the length of arc A?

Possible Answers:

Correct answer:

Explanation:

Circumference of a Circle = 

Arc Length

Example Question #171 : High School Math

Solve for .

Question_10

(Figure not drawn to scale).

Possible Answers:

Correct answer:

Explanation:

We can solve for the angle, , by using the below relationship.

In the figure, intercepted arc is given.

 

Example Question #1 : How To Find The Angle Of A Sector

A pie has a diameter of 12". A piece is cut out, having a surface area of 4.5π. What is the angle of the cut?

Possible Answers:

25°

45°

90°

4.5°

12.5°

Correct answer:

45°

Explanation:

This is simply a matter of percentages. We first have to figure out what percentage of the surface area is represented by 4.5π. To do that, we must calculate the total surface area. If the diameter is 12, the radius is 6. Don't be tricked by this!

A = π * 6 * 6 = 36π

Now, 4.5π is 4.5π/36π percentage or 0.125 (= 12.5%)

To figure out the angle, we must take that percentage of 360°:

0.125 * 360 = 45°

Example Question #1 : How To Find The Angle Of A Sector

Eric is riding a Ferris wheel. The Ferris wheel has 18 compartments, numbered in order clockwise. If compartment 1 is at 0 degrees and Eric enters compartment 13, what angle is he at?

Possible Answers:

260

240

180

280

300

Correct answer:

240

Explanation:

12 compartments further means 240 more degrees. 240 is the answer.

360/12 = 240 degrees

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