GMAT Math : Lines

Study concepts, example questions & explanations for GMAT Math

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Example Questions

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Example Question #1 :Geometry

Data Sufficiency Question

Is Line A perpendicular to the following line?

Statement 1: The slope of Line A is 3.

Statement 2: Line A passes through the point (2,3).

Possible Answers:

Each statement alone is sufficient.

Statements 1 and 2 together are not sufficient, and additional data is needed to answer the question.

Statement 1 alone is sufficient, but Statement 2 alone is not sufficient to answer the question.

Both statements taken together are sufficient to answer the question, but neither statement alone is sufficient.

Statement 2 alone is sufficient, but Statement 1 alone is not sufficient to answer the question.

Correct answer:

Statement 1 alone is sufficient, but Statement 2 alone is not sufficient to answer the question.

Explanation:

To determine if two lines are perpendicular, only the slope needs to be considered. The slopes of perpendicular lines are the negative reciprocals of each other. Knowing a single point on the line is not sufficient, as an infinite number of lines can pass through and individual point.

Example Question #1 :Geometry

Untitled

Refer to the above figure. True or false:

Statement 1:is equilateral.

Statement 2: Linebisects.

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.

EITHER statement ALONE is 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.

Correct answer:

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

Explanation:

Statement 1 alone establishes nothing about the anglemakes with, as it is not part of the triangle. Statement 2 alone only establishes that.

Assume both statements are true. Thenis an altitude of an equilateral triangle, making it - and- perpendicular with the base- and.

Example Question #3 :Geometry

UntitledStatement 1:

Refer to the above figure. Are the lines perpendicular?

Statement 1:

Statement 2:

Possible Answers:

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.

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.

Correct answer:

EITHER statement ALONE is sufficient to answer the question.

Explanation:

Assume Statement 1 alone. The measure of one of the angles formed is

degrees.

Assume Statement 2 alone.

By substitutingfor, one angle measure becomes

The marked angles are a linear pair and thus their angle measures add up to 180 degrees; therefore, we can set up an equation:

or

yields illegal angle measures - for example,

yields angle measuresfor both angles; the angles are right and the lines are perpendicular.

Example Question #4 :Geometry

Transversal

Refer to the above figure.

True or false:

Statement 1:

Statement 2:

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:

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

Explanation:

Statement 1 alone establishes by definition that, but does not establish any relationship betweenand.

By Statement 2 alone, since alternating interior angles are congruent,, but no conclusion can be drawn about the relationship of, since the actual measures of the angles are not given.

Assume both statements are true. By Statement 2,.andare corresponding angles formed by a transversal across parallel lines, so.is not a right angle, so.

Example Question #5 :Geometry

Untitled

Refer to the above figure. True or false:

Statement 1:

Statement 2: Linebisects.

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:

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

Explanation:

Assume Statement 1 alone. Then, as a consequence of congruence,andare congruent. They form a linear pair of angles, so they are also supplementary. Two angles that are both congruent and supplementary must be right angles, so.

Assume Statement 2 alone. Then, but without any other information about the angles thatormake with, it cannot be determined whetheror not.

Example Question #6 :Geometry

The equations of two lines are:

Are these lines perpendicular?

Statement 1:

Statement 2:

Possible Answers:

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.

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:

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

Explanation:

The lines of the two equations must have slopes that are the opposites of each others reciprocals.

写每一个方程斜截式:

As can be seen, knowing the value ofis necessary and sufficient to answer the question. The value ofis irrelevant.

The answer is that Statement 1 alone is sufficient to answer the question, but Statement 2 alone is not sufficient to answer the question.

Example Question #1 :Geometry

Lines

Note: Figure NOT drawn to scale.

Evaluate.

Statement 1:

Statement 2:

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.

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.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question.

Explanation:

Even with both statements,cannot be determined because the length of不见了。

For example, we can haveand, making; or, we can haveand, making. Neither scenario violates the conditions given.

Example Question #2 :Geometry

,, andare distinct points.

True or false:andare opposite rays.

Statement 1:is on

Statement 2:is on

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.

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.

EITHER statement ALONE is sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question.

Explanation:

Both statements are equivalent, as both are equivalent to stating that,, andare collinear. Therefore, it suffices to determine whether the fact that the points are collinear is sufficient to answer the question.

Rays

In both of the above figures,,, andare collinear, so the conditions of both statements are met. But in the top figure,andare the same ray, sinceis on; in the bottom figure, sinceandare on opposite sides of,andare opposite rays.

Example Question #1 :Dsq: Understanding Rays

,, andare distinct points.

True or false:andare opposite rays.

Statement 1:.

Statement 2:is the midpoint of.

Possible Answers:

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.

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:

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

Explanation:

We show Statement 1 alone is insufficient to determine whether the two rays are the same by looking at the figures below. In the first figure,is the midpoint of.

Rays

In both figures,. But only in the second figure,andare on the opposite side of the line from, so only in the second figure,andare opposite rays.

Assume Statement 2 alone. Ifis the midpoint of, then, as seen in the top figure,is on. Therefore,andare thesameray, not opposite rays.

Example Question #10 :Geometry

,, andare distinct points.

True or false:andare opposite rays.

Statement 1:

Statement 2:

Possible Answers:

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.

EITHER 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:

Statement 1 alone does not answer the question.

Case 1: Examine the figure below.

Rays

,

thereby meeting the condition of Statement 1.

Also,andare opposite rays, sinceandare on opposite sides of the same line from.

案例2:假设,, andare noncollinear.

The three points are vertices of a triangle, and by the Triangle Inequality Theorem,

.

Furthermore,andare not part of the same line and are not opposite rays.

Now assume Statement 2 alone. As can be seen in the diagram above, ifandare opposite rays, then by segment addition,, making Statement 2 false. Contrapositively, if Statement 2 holds, and, thenandare not opposite rays.

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