GMAT Math : GMAT Quantitative Reasoning

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #2 : Calculating Whether Lines Are Perpendicular

A given line  has a slope of . What is the slope of any line perpendicular to ?

Possible Answers:

Not enough information provided

Correct answer:

Explanation:

In order for a line  to be perpendicular to another line  defined by the equation  , the slope of line  must be a negative reciprocal of the slope of line . Since line 's slope is  in the slope-intercept equation above, line 's slope would therefore be .

Given that we have a line  with a slope , we can therefore conclude that any perpendicular line would have a slope .

Example Question #3 : Calculating Whether Lines Are Perpendicular

Which of the following lines are perpendicular to ?

Possible Answers:

Two answers are perpendicular to the given line.

Correct answer:

Two answers are perpendicular to the given line.

Explanation:

In order for a line  to be perpendicular to another line  defined by the equation  , the slope of line  must be a negative reciprocal of the slope of line . Since line 's slope is  in the slope-intercept equation above, line 's slope would therefore be .

Since in this instance the slope . Two of the above answers have this as their slope, so therefore that is the answer to our question.

Example Question #4 : Calculating Whether Lines Are Perpendicular

Do the functions  and  intersect at a ninety-degree angle, and how can you tell?

Possible Answers:

It is impossible to determine from the information provided.

Yes, because  and  have the same y-intercept.

No, because  and  never intersect.

Yes, because the slope of  is the reciprocal of the slope of  and it has the opposite sign.

No, because  and  have different slopes.

Correct answer:

Yes, because the slope of  is the reciprocal of the slope of  and it has the opposite sign.

Explanation:

If two lines intersect at a ninety-degree angle, they are said to be perpendicular. Two lines are perpendicular if their slopes are opposite reciprocals. In this case:

The two lines' slopes are reciprocals with opposing signs, so the answer is yes. Of our two yes answers, only one has the right explanation. Eliminate the option dealing with -intercepts.

Example Question #5 : Calculating Whether Lines Are Perpendicular

Find the slope of a line that is perpendicular to the line running through the points  and 

Possible Answers:

Not enough information provided.

Correct answer:

Explanation:

To find the slope  of the line running through  and , we use the following equation:

The slope of any line perpendicular to the given line would have a slope that is the negative reciprocal of , or . Therefore, 

Example Question #11 : Lines

Which of the following lines is perpendicular to 

Possible Answers:

Not enough information provided.

Correct answer:

Explanation:

Given a line  defined by the equation  with a slope of , any line perpendicular to  would have a slope that is the negative reciprocal of , . Given our equation  , we know that  and that 

The only answer choice with this slope is 

Example Question #12 : Lines

Which of the following lines is perpendicular to 

Possible Answers:

Two of the answers are correct.

Correct answer:

Two of the answers are correct.

Explanation:

Given a line  defined by the equation  with a slope of , any line perpendicular to  would have a slope that is the negative reciprocal of . Given our equation  , we know that  and that 

There are two answer choices with this slope,  and  . 

Example Question #13 : Lines

A given line  is defined by the equation . Which of the following lines would be perpendicular to line ?

Possible Answers:

Not enough information provided 

Correct answer:

Explanation:

For any line  with an equation  and slope , a line that is perpendicular to  must have a slope of , or the negative reciprocal of . Given , we know that  and therefore know that 

Only one equation above has a slope of 

Example Question #14 : Lines

What is the slope of a line that is perpendicular to 

Possible Answers:

Correct answer:

Explanation:

For any line  with an equation  and slope , a line that is perpendicular to  must have a slope of , or the negative reciprocal of . Given the equation , we know that  and therefore know that .

Example Question #15 : Lines

Which of the following lines is perpendicular to ?

Possible Answers:

None of the lines is perpendicular

Two lines are perpendicular 

Correct answer:

Two lines are perpendicular 

Explanation:

For any line  with an equation  and slope , a line that is perpendicular to  must have a slope of , or the negative reciprocal of . Given the equation , we know that  and therefore know that 

Given a slope of , we know that there are two solutions provided:  and 

Example Question #16 : Calculating Whether Lines Are Perpendicular

What is the slope of a line perpendicular to that of 

Possible Answers:

Correct answer:

Explanation:

First, we need to rearrange the equation into slope-intercept form.  .

  Therefore, the slope of this line equals  Perpendicular lines have slope that are the opposite reciprocal, or 

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