GRE Math : Parallel Lines

Study concepts, example questions & explanations for GRE Math

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Example Questions

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Example Question #21 :Coordinate Geometry

A certain line has points atand. Which of the following lines is parallel to the so-called "certain" line?

Possible Answers:

Correct answer:

Explanation:

To begin, we must first solve the for the slope of the original line. Use the formula for slope to do this:

Use the two points we were given:

Reduce the fraction:

We are looking for any answer choice with a slope of. The answer is.

Example Question #1 :How To Find Out If Lines Are Parallel

的re are two lines:

2x – 4y = 33

2x + 4y = 33

Are these lines perpendicular, parallel, non-perpendicular intersecting, or the same lines?

Possible Answers:

的same

None of the other answers

Parallel

Non-perpendicular intersecting

Perpendicular

Correct answer:

Non-perpendicular intersecting

Explanation:

To be totally clear, solve both lines in slope-intercept form:

2x – 4y = 33; –4y = 33 – 2x; y = –33/4 + 0.5x

2x + 4y = 33; 4y = 33 – 2x; y = 33/4 – 0.5x

的se lines are definitely not the same. Nor are they parallel—their slopes differ. Likewise, they cannot be perpendicular (which would require not only opposite slope signs but also reciprocal slopes); therefore, they are non-perpendicular intersecting.

Example Question #1 :How To Find Out If Lines Are Parallel

Which of the above-listed lines are parallel?

Possible Answers:

and

and

None of them

All four lines

,, and

Correct answer:

,, and

Explanation:

的re are several ways to solve this problem. You could solve all of the equations for. This would give you equations in the form. All of the lines with the samevalue would be parallel. Otherwise, you could figure out the ratio oftowhen both values are on the same side of the equation. This would suffice for determining the relationship between the two. We will take the first path, though, as this is most likely to be familiar to you.

Let's solve each for:

Here, you need to be a bit more manipulative with your equation. Multiply the numerator and denominator of thevalue by:

的refore,,, andall have slopes of

Example Question #212 :Geometry

Which of the following is parallel to the line passing throughand?

Possible Answers:

Correct answer:

Explanation:

Now, notice that the slope of the line that you have been given is. You know this because slope is merely:

However, for your points, there is no rise at all. You do not even need to compute the value. You know it will be. All lines with slopeare of the form, whereis the value thathas for allpoints. Based on our data, this is, foris always—no matter what is the value for. So, the parallel answer choice is, as both have slopes of.

Example Question #213 :Geometry

Which of the following is parallel to?

Possible Answers:

的line between the pointsand

的line between the pointsand

的line between the pointsand

的line between the pointsand

的line between the pointsand

Correct answer:

的line between the pointsand

Explanation:

To begin, solve your equation for. This will put it into slope-intercept form, which will easily make the slope apparent. (Remember, slope-intercept form is, whereis the slope.)

Divide both sides byand you get:

因此,斜率是. Now, you need to test your points to see which set of points has a slope of. Remember, for two pointsand, you find the slope by using the equation:

For our question, the pairandgives us a slope of:

Example Question #224 :New Sat

Which of the following lines is parallel to:

Possible Answers:

Correct answer:

Explanation:

First write the equation in slope intercept form. Addto both sides to get. Now divide both sides byto get. The slope of this line is, so any line that also has a slope ofwould be parallel to it. The correct answer is.

Example Question #1 :How To Find Out If Lines Are Parallel

Which pair of linear equations represent parallel lines?

Possible Answers:

y=x+2

y=-x+2

y=2x-4

y=2x+5

y=x-5

y=3x+5

y=-x+4

y = x + 6

y=2x+4

y = x + 4

Correct answer:

y=2x-4

y=2x+5

Explanation:

平行线永远山坡上平等。的slope can be found quickly by observing the equation in slope-intercept form and seeing which number falls in the "m" spot in the linear equation(y=mx+b),

We are looking for an answer choice in which both equations have the samemvalue. Both lines in the correct answer have a slope of 2, therefore they are parallel.

Example Question #2 :How To Find Out If Lines Are Parallel

Which of the following equations represents a line that is parallel to the line represented by the equation?

Possible Answers:

Correct answer:

Explanation:

Lines are parallel when their slopes are the same.

First, we need to place the given equation in the slope-intercept form.

Because the given line has the slope of, the line parallel to it must also have the same slope.

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