SSAT Upper Level Math : Geometry

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

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Example Questions

Example Question #231 : Geometry

Find the equation of the line that passes through the point \(\displaystyle (-2, 5)\) and is parallel to the line with the equation \(\displaystyle y=-x-2\).

Possible Answers:

\(\displaystyle y=x-4\)

\(\displaystyle y=x+3\)

\(\displaystyle y=-x+3\)

\(\displaystyle y=-x+6\)

Correct answer:

\(\displaystyle y=-x+3\)

Explanation:

Because the two lines are parallel, we know that the slope of the line we need to find must also be \(\displaystyle -1\).

Next, plug in the point given by the question to find the y-intercept of the line.

\(\displaystyle 5=-1(-2)+b\)

\(\displaystyle b+2=5\)

\(\displaystyle b=3\)

Now, we can write the equation for the line: \(\displaystyle y=-x+3\)

Example Question #175 : Coordinate Geometry

Find the equation of the line that passes through the point \(\displaystyle (-2, 3)\) and is parallel to the line with the equation \(\displaystyle y=\frac{1}{2}x-2\).

Possible Answers:

\(\displaystyle y=2x-1\)

\(\displaystyle y=-2x+4\)

\(\displaystyle y=\frac{1}{2}x-2\)

\(\displaystyle y=\frac{1}{2}x+4\)

Correct answer:

\(\displaystyle y=\frac{1}{2}x+4\)

Explanation:

Because the two lines are parallel, we know that the slope of the line we need to find must also be \(\displaystyle \frac{1}{2}\).

 

Next, plug in the point given by the question to find the y-intercept of the line.

\(\displaystyle 3=\frac{1}{2}(-2)+b\)

\(\displaystyle b-1=3\)

\(\displaystyle b=4\)

Now, we knwo the equation of the line must be \(\displaystyle y=\frac{1}{2}x+4\).

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

Find the equation of the line that passes through the point \(\displaystyle (2, 8)\) and is parallel to the line with the equation \(\displaystyle y=4x-1\).

Possible Answers:

\(\displaystyle y=4x\)

\(\displaystyle y=4x-2\)

\(\displaystyle y=-\frac{1}{4}x\)

\(\displaystyle y=\frac{1}{4}x+2\)

Correct answer:

\(\displaystyle y=4x\)

Explanation:

Because the two lines are parallel, we know that the slope of the line we need to find must also be \(\displaystyle 4\).

Next, plug in the point given by the question to find the y-intercept of the line.

\(\displaystyle 8=4(2)+b\)

\(\displaystyle b+8=8\)

\(\displaystyle b=0\)

Thus, the equation of the line must be \(\displaystyle y=8x\).

Example Question #177 : Coordinate Geometry

Find the equation of the line that passes through the point \(\displaystyle (10, 2)\) and is parallel to the line with the equation \(\displaystyle y=\frac{1}{5}x-2\).

Possible Answers:

\(\displaystyle y=\frac{1}{5}x\)

\(\displaystyle y=5x-1\)

\(\displaystyle y=-5x+2\)

\(\displaystyle y=\frac{1}{5}x-6\)

Correct answer:

\(\displaystyle y=\frac{1}{5}x\)

Explanation:

Because the two lines are parallel, we know that the slope of the line we need to find must also be \(\displaystyle \frac{1}{5}\).

Next, plug in the point given by the question to find the y-intercept of the line.

\(\displaystyle 2=\frac{1}{5}(10)+b\)

\(\displaystyle b+2=2\)

\(\displaystyle b=0\)

The equation of the line is \(\displaystyle y=\frac{1}{5}x\).

Example Question #181 : Coordinate Geometry

Find the equation of the line that passes through the point \(\displaystyle (3, 1)\) and is parallel to the line with the equation \(\displaystyle y=\frac{1}{3}x-9\).

Possible Answers:

\(\displaystyle y=\frac{1}{3}x+2\)

\(\displaystyle y=-\frac{1}{3}x\)

\(\displaystyle y=-3x\)

\(\displaystyle y=\frac{1}{3}x\)

Correct answer:

\(\displaystyle y=\frac{1}{3}x\)

Explanation:

Because the two lines are parallel, we know that the slope of the line we need to find must also be \(\displaystyle \frac{1}{3}\).

Next, plug in the point given by the question to find the y-intercept of the line.

\(\displaystyle 1=\frac{1}{3}(3)+b\)

\(\displaystyle b+1=1\)

\(\displaystyle b=0\)

The equation of the line is \(\displaystyle y=\frac{1}{3}x\).

Example Question #51 : Parallel Lines

Find the equation of the line that passes through the point \(\displaystyle \left(\frac{1}{2}, 4\right)\) and is parallel to the line with the equation \(\displaystyle y=2x-1\).

Possible Answers:

\(\displaystyle y=\frac{1}{2}x+2\)

\(\displaystyle y=2x+3\)

\(\displaystyle y=-\frac{1}{2}x-2\)

\(\displaystyle y=2x-2\)

Correct answer:

\(\displaystyle y=2x+3\)

Explanation:

Because the two lines are parallel, we know that the slope of the line we need to find must also be \(\displaystyle 2\).

Next, plug in the point given by the question to find the y-intercept of the line.

\(\displaystyle 4=\frac{1}{2}(2)+b\)

\(\displaystyle b+1=4\)

\(\displaystyle b=3\)

Now, we know the equation of the line must be \(\displaystyle y=2x+3\).

Example Question #52 : Parallel Lines

Find the equation of the line that passes through the point \(\displaystyle \left(2, \frac{1}{4}\right)\) and is parallel to the line with the equation \(\displaystyle y=\frac{1}{8}x-2\).

Possible Answers:

\(\displaystyle y=\frac{1}{8}x-8\)

\(\displaystyle y=-8x\)

\(\displaystyle y=\frac{1}{8}x\)

\(\displaystyle y=\frac{1}{8}x+3\)

Correct answer:

\(\displaystyle y=\frac{1}{8}x\)

Explanation:

Because the two lines are parallel, we know that the slope of the line we need to find must also be  \(\displaystyle \frac{1}{8}\).

Next, plug in the point given by the question to find the y-intercept of the line.

\(\displaystyle \frac{1}{4}=\frac{1}{8}(2)+b\)

\(\displaystyle b+\frac{1}{4}=\frac{1}{4}\)

\(\displaystyle b=0\).

We can then write the equation of the line: \(\displaystyle y=\frac{1}{8}x\)

 

Example Question #5 : How To Find The Equation Of A Parallel Line

Which of these formulas could be a formula for a line perpendicular to the line \(\displaystyle 2x + 3y = 16\)?

Possible Answers:

\(\displaystyle 6y - 9x = 16.5\)

\(\displaystyle 4x + 6y = 24\)

\(\displaystyle 6y + 9x = 16\)

\(\displaystyle 3y - 4x = 23\)

\(\displaystyle 4y - 9x = 24\)

Correct answer:

\(\displaystyle 6y - 9x = 16.5\)

Explanation:

This is a two-step problem. First, the slope of the original line needs to be found. The slope will be represented by "\(\displaystyle m\)" when the line is in \(\displaystyle y\)-intercept form \(\displaystyle (y=mx+b)\).

\(\displaystyle 2x +3y = 16\)

\(\displaystyle 3y = -2x +16\)

\(\displaystyle y = \left(\frac{-2}{3}\right)x +\left(\frac{16}{3}\right)\)

So the slope of the original line is \(\displaystyle -\frac{2}{3}\). A line with perpendicular slope will have a slope that is the inverse reciprocal of the original. So in this case, the slope would be \(\displaystyle \frac{3}{2}\). The second step is finding which line will give you that slope. For the correct answer, we find the following:

\(\displaystyle 6y - 9x = 16.5\)

\(\displaystyle 6y = 9x +16.5\)

\(\displaystyle y= \left(\frac{3}{2}x\right) +\left(\frac{16.5}{6}\right)\)

So, the slope is \(\displaystyle \frac{3}{2}\), and this line is perpendicular to the original.

Example Question #461 : Ssat Upper Level Quantitative (Math)

Find the equation of a line that goes through the point \(\displaystyle (0, 4)\) and is parallel to the line with the equation \(\displaystyle y=4x-2\).

Possible Answers:

\(\displaystyle y=4x-4\)

\(\displaystyle y=4x+4\)

\(\displaystyle y=\frac{1}{4}x-4\)

\(\displaystyle y=-4x+4\)

Correct answer:

\(\displaystyle y=4x+4\)

Explanation:

For lines to be parallel, they must have the same slope. The slope of the line we are looking for then must be \(\displaystyle 4\).

The point that's given in the equation is also the y-intercept.

Using these two pieces of information, we know that the equation for the line must be \(\displaystyle y=4x+4\)

Example Question #181 : Lines

There is a circle on a coordinate plain. Its perimeter passes through the point \(\displaystyle (1,0)\). At this point meets a tangent line, which also passes through the point \(\displaystyle (5,7)\). What is the slope of the line perpindicular to this tangent line?
Possible Answers:

\(\displaystyle -\frac{7}{4}\)

\(\displaystyle \frac{7}{4}\)

\(\displaystyle \frac{4}{7}\)

\(\displaystyle -\frac{4}{7}\)

\(\displaystyle \frac{7}{6}\)

Correct answer:

\(\displaystyle -\frac{4}{7}\)

Explanation:

In this kind of problem, it's important to keep track of information given about your line of interest. In this case, the coordinates given set up the stage for us to be able to get to our line of focus - the line perpendicular to the tangent line. In order to determine the perpendicular line's slope, the tangent line's slope must be calculated. Keeping in mind that:

\(\displaystyle slope =\frac{rise}{run}=\frac{\Delta y}{\Delta x} =\frac{y_2-y_1}{x_2-x_1}\)

where y2,x2 and y1,x1 are assigned arbitrarily as long as the order of assignment is maintained. 

\(\displaystyle \frac{y_2-y_1}{x_2-x_1}=\frac{7-0}{5-1}=\frac{7}{4}\)  which is the slope of the tangent line.

To calculate the perpendicular line, we have to remember that the product of the tangent slope and the perpendicular slope will equal -1.

\(\displaystyle \frac{7}{4} x \frac{?}{?} = -1\), the perpendicular slope can then be calculated as \(\displaystyle \frac{-4}{7}\)

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