GMAT Math : GMAT Quantitative Reasoning

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #1 : Lines

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 #2 : Lines

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 #631 : Gmat Quantitative Reasoning

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

Possible Answers:

Yes, because  and  have the same y-intercept.

No, because  and  have different slopes.

It is impossible to determine from the information provided.

No, because  and  never intersect.

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

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 #10 : 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 #632 : Gmat Quantitative Reasoning

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:

Two lines are perpendicular 

None of the lines is 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 #11 : Lines

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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