GMAT Math : Calculating whether lines are parallel
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Example Questions
Example Question #1 : Parallel Lines
Which of the following pairs of lines are parallel?
Two lines are parallel if they have the same slope. Let's go through the answer choices.
1. 
2. 
3. 
4. 
5. 
Example Question #2 : Parallel Lines
Determine whether 
Yes, because the slopes are negative reciprocals of each other.
No, because the slopes are not negative reciprocals of each other.
Yes, because the slopes are the same.
No, because the slopes are not similar.
Yes, because the slopes are the same.
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.
Example Question #3 : Parallel Lines
Three lines - one green, one blue, one red - are drawn on the coordinate axes. They have the following characteristics:
The green line has 
The blue line has 
The red line has 
Which of these lines are parallel to each other?
Only the blue line and the green line are parallel to each other.
Only the blue line and the red line are parallel to each other.
All three lines are parallel to one another.
Only the green line and the red line are parallel to each other.
No two of these lines are parallel to each other.
Only the blue line and the red line are parallel to each other.
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.
Example Question #2 : Calculating Whether Lines Are Parallel
What is the slope of a line that is parallel to 
None of the above
Two lines are parallel if their slopes have the same value. Since 
Example Question #4 : Parallel Lines
Which of the following lines is parallel to 
Two of the answers provided are correct.
Two lines are parallel to each other if their slopes have the same value. Since the slope of 
Example Question #5 : Parallel Lines
Determine whether 
Yes, because the slopes are the same.
Cannot determine.
No, because the slopes are not negative reciprocals of each other.
Yes, because the slopes are negative reciprocals of each other.
No, because the slopes are not the same.
No, because the slopes are not the same.
By definition, lines that are parallel to each other must have the same slope. 
Example Question #36 : Coordinate Geometry
Tell whether the lines described by the following are parallel.
g(x) is a linear equation which passes through the points 
They are parallel, because their slopes are opposite reciprocals of each other.
There are not parallel, they are the same line.
They are not parallel, because they have different slopes.
They are parallel, because they have the same slope.
They are not parallel, because they have different slopes.
Tell whether the lines described by the following are parallel.
g(x) is a linear equation which passes through the points 
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!
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