SSAT Upper Level Math : Geometry

Study concepts, example questions & explanations for SSAT Upper Level Math

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Example Questions

Example Question #21 : X And Y Intercept

The -intercept and the only -intercept of a vertical parabola on the coordinate plane coincide with the -intercept and the -intercept of the line of the equation . Give the equation of the parabola.

Possible Answers:

Insufficient information is given to determine the equation.

Correct answer:

Explanation:

To find the -intercept, that is, the point of intersection with the -axis, of the line of equation , set  and solve for :

The -intercept is .

The -intercept can be found by doing the opposite:

The -intercept is .

The parabola has these intercepts as well. Also, since the vertical parabola has only one -intercept, that point doubles as its vertex as well. 

The equation of a vertical parabola, in vertex form, is

,

where  is the vertex. Set :

for some real . To find it, use the -intercept, setting 

The parabola has equation , which is rewritten as

Example Question #1 : How To Find The Equation Of A Curve

An ellipse on the coordinate plane has as its center the point . It passes through the points  and . Give its equation.

Possible Answers:

Insufficient information is given to determine the equation.

Correct answer:

Explanation:

The equation of the ellipse with center , horizontal axis of length , and vertical axis of length  is

The center is , so  and .

To find , note that one endpoint of the horizontal axis is given by the point with the same -coordinate through which it passes, namely, . Half the length of this axis, which is , is the difference of the -coordinates, so . Similarly, to find , note that one endpoint of the vertical axis is given by the point with the same -coordinate through which it passes, namely, . Half the length of this axis, which is , is the difference of the -coordinates, so .

The equation is 

or 

.

Example Question #11 : How To Find The Equation Of A Curve

An ellipse passes through points 

Give its equation.

Possible Answers:

Correct answer:

Explanation:

The equation of the ellipse with center , horizontal axis of length , and vertical axis of length  is

 and  are the endpoints of a horizontal line segment with midpoint

, or 

and length .

 and  are the endpoints of a vertical line segment with midpoint

, or 

and length 

Because their midpoints coincide, these are the endpoints of the horizontal axis and vertical axis, respectively, of the ellipse, and the common midpoint  is the center.

Therefore, 

 and ;

 and ; consequently  and .

The equation of the ellipse is 

, or

 

Example Question #512 : Ssat Upper Level Quantitative (Math)

A horizontal parabola on the coordinate plane   as its only -intercept; its -intercept is .

Give its equation.

Possible Answers:

Insufficient information is given to determine the equation.

Correct answer:

Explanation:

If a horizontal parabola has only one -intercept, which here is , that point doubles as its vertex as well. 

The equation of a horizontal parabola, in vertex form, is

,

where  is the vertex. Set :

To find , use the -intercept, setting :

The equation, in vertex form, is . In standard form:

 

Example Question #511 : Ssat Upper Level Quantitative (Math)

A horizontal parabola on the coordinate plane has vertex ; one of its -intercepts is .

Give its equation.

Possible Answers:

Insufficient information is given to determine the equation.

Correct answer:

Explanation:

The equation of a horizontal parabola, in vertex form, is

,

where  is the vertex. Set :

To find , use the known -intercept, setting :

The equation, in vertex form, is ; in standard form:

Example Question #512 : Ssat Upper Level Quantitative (Math)

A vertical parabola on the coordinate plane has -intercepts  and , and passes through .

Give its equation.

Possible Answers:

Insufficient information is given to determine the equation.

Correct answer:

Explanation:

A horizontal parabola which passes through   and  has as its equation

.

To find , substitute the coordinates of the third point, setting :

The equation is therefore , which is, in standard form:

Example Question #515 : Ssat Upper Level Quantitative (Math)

A vertical parabola on the coordinate plane has -intercepts  and , and passes through .

Give its equation.

Possible Answers:

Correct answer:

Explanation:

A vertical parabola which passes through  and  has as its equation

To find , substitute the coordinates of the third point, setting :

The equation is ; expand to put it in standard form:

Example Question #12 : How To Find The Equation Of A Curve

A horizontal parabola on the coordinate plane has -intercept ; one of its -intercepts is .

Give its equation.

Possible Answers:

Insufficient information is given to determine the equation.

Correct answer:

Insufficient information is given to determine the equation.

Explanation:

The equation of a horizontal parabola, in standard form, is

for some real 

 is the -coordinate of the -intercept, so , and the equation is

Set :

However, no other information is given, so the values of  and  cannot be determined for certain. The correct response is that insufficient information is given.

Example Question #13 : How To Find The Equation Of A Curve

A vertical parabola on the coordinate plane includes points  and 

Give its equation.

Possible Answers:

Correct answer:

Explanation:

The standard form of the equation of a vertical parabola is

If the values of  and  from each ordered pair are substituted in succession, three equations in three variables are formed:

 

 

 

The system

can be solved through the elimination method.

First, multiply the second equation by  and add to the third:

         

 

Next, multiply the second equation by  and add to the first:

          

Which can be divided by 3 on both sides to yield

 

Now solve the two-by-two system

by substitution:

Back-solve:

Back-solve again:

The equation of the parabola is therefore 

.

Example Question #14 : How To Find The Equation Of A Curve

A vertical parabola on the coordinate plane shares one -intercept with the line of the equation , and the other with the line of the equation . It also passes through . Give the equation of the parabola.

Possible Answers:

The correct answer is not among the other responses.

Correct answer:

Explanation:

First, find the -intercepts—the points of intersection with the -axis—of the lines by substituting 0 for  in both equations.

 is the -intercept of this line. 

 is the -intercept of this line. 

The parabola has -intercepts at  and , so its equation can be expressed as 

for some real . To find it, substitute using the coordinates of the third point, setting :

.

The equation is , which, in standard form, can be rewritten as:

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