Calculating whether lines are parallel - GMAT Quantitative Reasoning

Card 0 of 7

Question

Determine whether and are parallel lines.

Answer

Parallel lines have the same slope. Therefore, we need to find the slope once both equations are in slope intercept form :

The lines are parallel because the slopes are the same.

Compare your answer with the correct one above

Question

Which of the following pairs of lines are parallel?

Answer

Two lines are parallel if they have the same slope. Let's go through the answer choices.

1. and : Both slopes are 3, parallel.

2. and : Slopes are 2 and 3, not parallel.

3. and : We need to put these two equations into the form of to find the slope, .

3x - 2y=5\Rightarrow -2y=5-3x\Rightarrow y=3x/2-5/2, so the first slope is .

2x+3y=4\Rightarrow 3y=4-2x\Rightarrow y=-2x/3 + 4/3, so the second slope is . These lines are perpendicular, not parallel.

4. and : Slopes are undefined and 0, respectively, so not parallel.

5. and : Let's again put these into the form of .

5x+4y=1\Rightarrow 4y=1-5x\Rightarrow y=-5x/4 + 1/4, so the first slope is .

4x+5y=2\Rightarrow 5y=2-4x\Rightarrow y=-4x/5+2/5, so the second slope is . The lines are not parallel.

Compare your answer with the correct one above

Question

Three lines - one green, one blue, one red - are drawn on the coordinate axes. They have the following characteristics:

The green line has -intercept and -intercept .

The blue line has -intercept and -intercept .

The red line has -intercept and -intercept .

Which of these lines are parallel to each other?

Answer

Use the intercepts to find the slopes of the lines.

Green:

Blue:

Red:

The blue and red lines have the same slope; the green line has a different slope from the other two. That means only the blue and red lines are parallel.

Compare your answer with the correct one above

Question

Which of the following lines is parallel to ?

Answer

Two lines are parallel to each other if their slopes have the same value. Since the slope of is , is the only other line provided that has the same slope.

Compare your answer with the correct one above

Question

Determine whether and are parallel lines.

Answer

By definition, lines that are parallel to each other must have the same slope. has a slope of and has a slope of , therefore they are not parallel because their slopes are not the same.

Compare your answer with the correct one above

Question

What is the slope of a line that is parallel to ?

Answer

Two lines are parallel if their slopes have the same value. Since has a slope of , any line parallel to it must also have a slope of .

Compare your answer with the correct one above

Question

Tell whether the lines described by the following are parallel.

g(x) is a linear equation which passes through the points and .

Answer

Tell whether the lines described by the following are parallel.

g(x) is a linear equation which passes through the points and

Begin by recalling that lines are parallel if their slopes are the same and they have different y-intercepts.

Let's find the slope of g(x)

Note that this slope is not the same as f(x), so we do not have parallel lines!

Compare your answer with the correct one above

Tap the card to reveal the answer