GMAT Math : Data-Sufficiency Questions

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #661 : Data Sufficiency Questions

True or false: , and  are collinear points.

Statement 1: 

Statement 2:  and 

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 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.

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. 

The proportion statement

can be rewritten by setting the reciprocals of the expressions equal:

The first expression is the slope of the line through  and ; the second is the slope of the line through  and . Since the slopes are equal, the three points are on the same line - collinear.

The three points cannot be assumed to be collinear from Statement 2 alone. For example, , and  collectively fit the condition of Statement 2, and all three points are easily seen to be on the line of the equation . However,  , and  collectively fit the condition of Statement 2, and while the line through the first two points is again  is off that line, so the three points are noncollinear.

Example Question #5 : Dsq: Graphing A Point

True or false:  and  are in the same quadrant of the rectangular coordinate plane.

Statement 1:  and  are of different sign.

Statement 2:  and  are of different sign.

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.

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.

Correct answer:

EITHER statement ALONE is sufficient to answer the question.

Explanation:

Two points in the same quadrant have -coordinates of the same sign and -coordinates of the same sign; however, from Statement 1 alone, we find that the  -coordinates of the points have different signs, and from Statement 2 alone, we find that this holds for the -coordinates. Therefore, from either statement alone, the points can be proved to be in different quadrants.

Example Question #6 : Dsq: Graphing A Point

In which quadrant is the point  located: I, II, III, or IV?

Statement 1: 

Statement 2: 

Possible Answers:

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. 

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:

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

Explanation:

Assume Statement 1 alone. The set of points that satisfy the equation is the set of all points on the line of the equation 

which will pass through at least two quadrants on the coordinate plane. Therefore, Statement 1 provides insufficient information.

Now assume Statement 2 alone. The set of points that satisfy the equation is the set of all points of the circle of the equation

This circle has  as its center and  as its radius. Since its center is , which is 5 units away from its closest axis, and the radius is less than 5 units, the circle never intersects an axis, so it is contained entirely within the same quadrant as its center. The center has negative - and -coordinates, placing it, and the entire circle, in Quadrant III.

Example Question #7 : Dsq: Graphing A Point

In which quadrant is the point  located: I, II, III, or IV?

Statement 1: 

Statement 2: 

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 sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

BOTH statements TOGETHER are insufficient 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:

Assume both statements. The points  and  each satisfy the conditions of both statements, since , and . The former is in Quadrant I, having a positive -coordinate and a positive -coordinate; the latter is in Quadrant IV, having a positive -coordinate and a negative -coordinate.

Example Question #8 : Dsq: Graphing A Point

True or false: , and  are collinear points.

Statement 1:  and 

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.

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.

Correct answer:

EITHER statement ALONE is sufficient to answer the question.

Explanation:

Assume Statement 1 alone. The equations can be rewritten as follows:

 

The - and -coordinates of  are the arithmetic means of those of  and  , so  is the midpoint of the segment with those endpoints. Therefore, the three points are collinear.

Assume Statement 2 alone. The statement can be rewritten as follows:

The first expression is the slope of the line through  and ; the second expression is the slope of the line through  and . Since the slopes are equal, the three points are collinear.

Example Question #661 : Data Sufficiency Questions

What quadrant contains the point  , where  ?

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.

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.

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:

Statement 1 alone tells you that  and  are of the same sign, so the point is in Quadrant I (both positive) or Quadrant III (both negative).

Statement 2 tells you that any of the following hold:

 is positive and  is negative - example: 

 is negative and  is negative - example: 

 is positive and  is positive - example: 

This places the point in any quadrant except Quadrant II (where  is negative and  is positive). 

The two statements together only eliminate two quadrants and leave both Quadrant I and Quadrant III as possibilities.

Example Question #2 : Dsq: Graphing An Ordered Pair

Graph the point .

I)  is in quadrant IV.

II)  .

Possible Answers:

Either statement is sufficient to answer the question.

Both statements are needed to answer the question.

Neither statement is sufficient to answer the question. More information is needed.

Statement II is sufficient to answer the question, but statement I is not sufficient to answer the question.

Statement I is sufficient to answer the question, but statement II is not sufficient to answer the question.

Correct answer:

Both statements are needed to answer the question.

Explanation:

Graph the point (a,b)

I) (a,b) is in quadrant 4

II)  

To graph (a,b) we need to know a and b

I) Tells us which quadrant the point is in. In quadrant 4, the x value is positive and the y value must be negative.

II) Lets us find the following:

So the only possible location of  is .

Therefore, both statements are needed to answer the question. 

Example Question #1 : Dsq: Graphing An Exponential Function

Graph the exponential function .

I)  is a monomial.

II)  has a base of 4.

Possible Answers:

Either statement is sufficient to answer the question.

Statement I is sufficient to answer the question, but Statement II is not sufficient to answer the question.

Both statements are needed to answer the question.

Statement II is sufficient to answer the question, but Statement I is not sufficient to answer the question.

Neither statement is sufficient to answer the question. More information is needed.

Correct answer:

Neither statement is sufficient to answer the question. More information is needed.

Explanation:

An exponential function follows the general form of

Statement I tells us that there is only one term, so the  part of the equation isn't needed for this exponential function.

Statement II tells us that in this case, .

However, we could have nearly anything as our exponent. We are unable to make an accurate graph of this function, so more information is needed.

Example Question #662 : Data Sufficiency Questions

The graph of the function  is a parabola. Is this parabola concave upward or is it concave downward?

Statement 1: 

Statement 2: 

Possible Answers:

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.

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.

Correct answer:

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

Explanation:

Whether the parabola of a quadratic function  is concave upward or concave downward depends on one thing and one thing only - whether quadratic coefficient  is positive or negative. Statement 1 gives you this information; Statement 2 does not.

Example Question #663 : Data Sufficiency Questions

What is the equation of the line of symmetry of a vertical parabola on the coordinate plane?

Statement 1: The -intercept of the parabola is .

Statement 2: The only -intercept of the parabola is at .

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.

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. 

Correct answer:

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

Explanation:

The line of symmetry of a vertical parabola is the vertical line passing through the vertex. Statement 1 alone is not helpful, since it only gives the -intercept.

Statement 2 alone, however, answers the question. In a parabola with only one -intercept, that -intercept, given in Statement 2 as , doubles as the vertex. The vertical line through the vertex, which here is the line with equation , is the line of symmetry.

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