GMAT Math : Geometry

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #661 : Geometry

Is the slope of a line on the coordinate plane positive, zero, negative, or undefined?

Statement 1: It includes the origin.

Statement 2: It passes through Quadrant II.

Possible Answers:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

EITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Explanation:

Infinitely many lines pass through the origin, and infinitely many lines pass through each quadrant, so neither statement alone is sufficient to answer the question.

Suppose that both statements are known to be true. Since the line passes through quadrant II, it passes through a point  , where  are positive. It also passes through  so its slope will be

which is a negative slope.

Example Question #662 : Geometry

A line is on the coordinate plane. What is its slope?

Statement 1: The line is parallel to the line of the equation .

Statement 2: The line is perpendicular to the line of the equation .

Possible Answers:

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

EITHER statement ALONE is sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

Correct answer:

EITHER statement ALONE is sufficient to answer the question.

Explanation:

If Statement 1 alone holds - that is, if it is known only that the line is parallel to the line of  - then this equation can be rewritten in slope-intercept form. The slope can be deduced from this, and the two lines, being parallel, will have the same slope.

If Statement 2 alone holds - that is, if it is known only that the line is perpendicular to the line of the equation  - then this equation can be rewritten in slope-intercept form. The slope can be deduced from this, and the first line, which is perpendicular to this one, will have the slope that is the opposite of the reciprocal of that.

Either statement alone will yield an answer.

Example Question #663 : Geometry

Is the slope of a line on the coordinate plane positive, zero, negative, or undefined?

Statement 1: The line contains points in both Quadrant I and Quadrant II.

Statement 2: The line contains points in both Quadrant I and Quadrant III.

Possible Answers:

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

EITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Correct answer:

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Explanation:

Examine the diagram below.

 Axes_3

It can be seen from the red lines that no conclusions about the sign of the slope of a line can be drawn from Statement 1, since lines of positive, negative, and zero slope can contain points in both Quadrant I and Quadrant II.

If a line contains a point in Quadrant I and a point in Quadrant III, then it contains a point with positive coordinates  and a point with negative coordinates ; its slope is

which is a positive slope. 

Therefore, Statement 2 alone, but not Statement 1 alone, provides a definitive answer.

Example Question #21 : Other Lines

Is the slope of a line on the coordinate plane positive, zero, negative, or undefined?

Statement 1: It passes through the point .

Statement 2: It passes through Quadrant III.

Possible Answers:

EITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question. 

Explanation:

Examine the diagram below.

Axes_3

Both the red line and the green line fit the descriptions in both statements. The red line has negative slope and the green line has positive slope. 

The two statements together give insufficient infomation.

Example Question #665 : Geometry

Quinn was challenged by his teacher to fill in the square, the triangle, and the circle in the diagram below with three numbers to form the equation of a line with slope .

Did Quinn succeed?

Statement 1: Quinn wrote a 3 in the square.

Statement 2: Quinn wrote a  in the triangle.

Possible Answers:

EITHER statement ALONE is sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Explanation:

The equation is in standard form, with shapes replacing coefficients; that is, the equation is

.

Rewrite the equation in slope-intercept form:

The slope of the line of the equation is  - and it depends on the number in the square, , and the triangle . Each statement alone gives the number in only one of the shapes; the two statements together give the numbers in both shapes and allow the slope to be calculated, thereby answering the question of Quinn's success.

Example Question #2891 : Gmat Quantitative Reasoning

Ava was challenged by her teacher to fill in the triangle, the square, and the circle in the diagram below with three numbers to form the equation of a line with slope 1.

Did Ava succeed?

Statement 1: Ava wrote a 1 in the circle.

Statement 2: Ava wrote the same positive number in both the triangle and the square. 

Possible Answers:

BOTH statements TOGETHER are insufficient to answer the question. 

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

EITHER statement ALONE is sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Correct answer:

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Explanation:

Replacing the shapes with variables, the template becomes

Divide by  to get the equation in slope-intercept form:

The slope is .

The slope is the ratio of the number in the square to the number in the triangle, so the number in the circle is irrelevant, making Statement 1 unhelpful.

Assume Statement 2 alone. Since the numbers in the square and the triangle are equal, , and . Ava succeeded.

Example Question #663 : Geometry

John's teacher gave him two equations, each with one coefficient missing, as follows:

John was challenged to write one number in each shape in order to form two equations whose lines have the same slope. Did he succeed?

Statement 1: The number John wrote in the box is three times the number he wrote in the circle.

Statement 2: John wrote  in the circle.

Possible Answers:

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

EITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Correct answer:

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Explanation:

Rewrite the two equations with variables rather than shapes:.

The first equation can be rewritten in slope-intercept form: 

Its line has slope is , so if the number in the square is known, the slope is known.

 

 

is already in slope-intercept form; its line has slope , the number in the circle.

 

Statement 2 alone gives the number in the circle but provides no clue to the number in the square.

Now assume Statement 1 alone. Then . The slope of the first line is 

,

the slope of the second line. Statement 1 provides sufficient proof that John was successful.

Example Question #666 : Geometry

Does a line on the coordinate plane have undefined slope?

Statement 1: It has -intercept 

Statement 2: It passes through Quadrant II.

Possible Answers:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

EITHER statement ALONE is sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Explanation:

A line with undefined slope is a vertical line.

Infinitely many lines, some vertical and some not, pass through , and infinitely many lines, some vertical and some not, pass through each quadrant, so neither statement alone is sufficient to answer the question.

Now assume both statements are true. Then, since the line passes through Quadrant II, it passes through at least one point with negative -coordinate and positive -coordinate, which we call . Its slope will be

,

a negative slope. Therefore, the slope is not undefined.

Example Question #781 : Data Sufficiency Questions

Tim was challenged by his teacher to fill in the square, the triangle, and the circle in the diagram below with three numbers to form the equation of a line with slope .

Did Tim succeed?

Statement 1: Tim wrote  in the square.

Statement 2: Tim wrote  in the circle.

Possible Answers:

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

EITHER statement ALONE is sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question. 

Explanation:

Assume both statements are true. The equation takes the form 

,

where  is the number Tim wrote in the triangle.

Put the equation in slope-intercept form:

The coefficient of , which is , is the slope. As can be seen, the value of —that is, the number Tim wrote in the triangle—needs to be known. However, this information is still not given. Whether Tim succeeded is unknown.

Example Question #22 : Other Lines

Marisol was challenged by her teacher to fill in the square and the circle in the diagram below with two numbers to form the equation of a line with slope .

Did Marisol succeed?

Statement 1: Marisol wrote a  in the box.

Statement 2: Marisol wrote a  in the circle.

Possible Answers:

EITHER statement ALONE is sufficient to answer the question.

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are insufficient to answer the question. 

Correct answer:

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Explanation:

The pattern shows a linear equation in slope-intercept form, , with slope  represented by the square and -intercept  represented by the circle. Statement 1 gives the slope, so it provides sufficient information; Statement 2 gives only the -intercept, so it is unhelpful.

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