HiSET: Math : Measurement and Geometry

Study concepts, example questions & explanations for HiSET: Math

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Example Questions

Example Question #11 : Dilations

On the graph of the equation 

,

perform a dilation with center  and scale factor 

Give the equation of the resulting circle.

Possible Answers:

None of the other choices gives the correct response.

Correct answer:

Explanation:

The graph of the equation

is a circle with center  and radius .

,

or

is a circle with  center at origin  and radius 8.

A dilation of a circle with scale factor  will result in multiplying that radius by , so the radius of the circle will be 

To find the center of the image, note that the origin is 4 units below . The center of the new circle must be  units below , so this center will be , or . See the figure below:

1

 

Substituting in the circle formula, this is 

,

or

.

Example Question #12 : Dilations

Obtuse triangle

On the above obtuse triangle perform a dilation of scale factor  with the center of the dilation at the circumcenter of the triangle. Let the images of , and  be ,  and , respectively.

Which of the following correctly shows  relative to  ?

Possible Answers:

Obtuse triangle

Obtuse triangle

Obtuse triangle

Obtuse triangle

1

Correct answer:

Obtuse triangle

Explanation:

The circumcenter of a triangle can be located by finding the intersection of the perpendicular bisectors of the three sides of the triangle. The perpendicular bisectors are shown below, with point of intersection  :

Obtuse triangle

Construct , and . A dilation of scale factor   with center  can be performed by letting , and  be the midpoints of , and , respectively: 

Obtuse triangle

Removing the perpendicular bisectors and , we see that the correct choice is the figure

Obtuse triangle

Example Question #141 : Hi Set: High School Equivalency Test: Math

Find the circumference of a circle with the following diameter:

Possible Answers:

Correct answer:

Explanation:

A circle's circumference is calculated using the following formula:

In this equation, the variable, , is the circle's radius.

In our problem we are given the diameter. The diameter is related to the radius in the following manner:

Let's rewrite our formula by substituting the diameter for the radius.

Let's substitute and solve.

Example Question #142 : Hi Set: High School Equivalency Test: Math

Which of the following is closest to the length of a 270-degree arc of a circle with radius 20?

Possible Answers:

Correct answer:

Explanation:

A circle with radius 20 has as its circumference times this, or

There are 360 degrees in a circle, so a 270-degree arc is

of the circle. Therefore, the length of this arc is

,

so a reasonable estimate of the length of this arc is

Of the five choices, 95 comes closest to the correct length.

Example Question #3 : Equations Of Circles

A circle on the coordinate plane has a diameter with endpoints and . Give its equation.

Possible Answers:

Insufficient information exists to determine its equation.

Correct answer:

Explanation:

The equation, in standard form, of a circle on the coordinate plane with center and radius is

.

It is necessary to find the center and the radius of the circle in order to determine its equation.

The center of the circle is the midpoint of a given diameter. The midpoint of a segment with endpoints  and  can be found by applying the midpoint formula:

Setting :

Setting

The midpoint, and the center of the circle, is at .

The radius of the circle is the distance from the center to an endpoint, so we can use the distance formula

.

Substitute :

and

Now, set in the standard form of the equation of a circle, and the result is

Example Question #4 : Equations Of Circles

A circle on the coordinate plane has a radius with endpoints and . Give its equation.

Possible Answers:

Insufficient information exists to determine its equation.

Correct answer:

Insufficient information exists to determine its equation.

Explanation:

The equation, in standard form, of a circle on the coordinate plane with center and radius is

.

It is necessary to find the center and the radius of the circle in order to determine its equation. The radius of the circle can be determined by applying the distance formula to the coordinates of the endpoints of the radius. However, it is not clear from the information given which endpoint is the center of the circle. Therefore, while can be determined, cannot. The correct response is that insufficient information exists to determine its equation.

Example Question #1 : Equations Of Circles

What is the circumference of a circle with an area of

Possible Answers:

Correct answer:

Explanation:

Step 1: Since we are given the area, let's first find the radius of the circle.

If the area of a circle is calculated by: , we can plug in the values that are given to us. .

We have . We will divide by .

. To find the radius, we will take the square root of both sides. 

So, .

Step 2: Now that we have the radius, we will now find the circumference.

The circumference formula by using the radius is .

Plug in all the information that we have...

 

Example Question #5 : Equations Of Circles

A circle on the coordinate plane has center  and circumference

Give its equation.

Possible Answers:

Correct answer:

Explanation:

The standard form of the equation of a circle with center at and radius is

The circumference of the circle is ; to find the radius, divide this circumference by :

Now, set in the equation of the circle:

Simplifying:

,

the correct equation.

Example Question #5 : Equations Of Circles

A circle on the coordinate plane has center  and area

Give its equation.

Possible Answers:

Correct answer:

Explanation:

The standard form of the equation of a circle with center at and radius is

The area  of the circle is ; to find the radius, substitute in the formula:

We do not need to find . Set  in the equation of the circle:

Simplifying:

,

the correct equation.

Example Question #141 : Hi Set: High School Equivalency Test: Math

A circle on the coordinate plane has its center at and passes through . Give its circumference.

Possible Answers:

The information given is insufficient to answer the question

Correct answer:

Explanation:

The radius of the circle is the distance between its center and a point that it passes through. This radius can be calculated using the distance formula:

.

Setting :

The circumference of a circle is equal to multiplied by the radius, so

,

the correct response.

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