GMAT Math : Data-Sufficiency Questions

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Example Question #241 : Data Sufficiency Questions

True or false: A+ B > 50

Statement 1: A rectangle with length and width has area greater than 100.

Statement 2: A rectangle with length and width has perimeter greater than 100.

Possible Answers:

STATEMENT 1 ALONE provides sufficient information to answer the question, but STATEMENT 2 ALONE does NOT provide sufficient information to answer the question.

STATEMENT 2 ALONE provides sufficient information to answer the question, but STATEMENT 1 ALONE does NOT provide sufficient information to answer the question.

BOTH STATEMENTS TOGETHER do NOT provide sufficient information to answer the question.

BOTH STATEMENTS TOGETHER provide sufficient information to answer the question, but NEITHER STATEMENT ALONE provides sufficient information to answer the question.

EITHER STATEMENT ALONE provides sufficient information to answer the question.

Correct answer:

STATEMENT 2 ALONE provides sufficient information to answer the question, but STATEMENT 1 ALONE does NOT provide sufficient information to answer the question.

Explanation:

Statement 1 alone provides insufficient information. For example:

Case 1: A = 10, B = 12

The area of a rectangle with these dimensions is their product, which is 120; this exceeds 100.

A + B = 10+12 = 22 < 50

Case 2: A =40, B = 12

The area of a rectangle with these dimensions is their product, which is 480; this exceeds 100.

A + B = 40+12 = 52 > 50

Assume Statement 2 alone. The perimeter of a rectangle is twice the sum of their dimensions, so

2(A+B)> 100

$\frac{2(A+B)}{2}> \frac{100}{2}$

A + B > 50 , answering the question in the affirmative.

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Example Question #241 : Data Sufficiency Questions

Rectangles

Note: Figure NOT drawn to scale.

Refer to the above figure, which shows a rectangle divided into two smaller rectangles.

True or false: $\textup{Rect } ABCF \sim \textup{Rect } CDEF$ .

Statement 1: $CF = \sqrt{AF \cdot FE}$

Statement 2: $AF \cdot FE = AB \cdot DE$

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 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.

Correct answer:

EITHER statement ALONE is sufficient to answer the question.

Explanation:

The statements are actually equivalent. Since CF = AB= DE , Statement 2 can be rewritten as $AF \cdot FE = CF \cdot CF$ , or $\left (CF \right )^{2} =AF \cdot FE$ - and, since all quantities are positive, $CF = \sqrt{AF \cdot FE}$ . The question is therefore whether either statement alone answers the question or both together do not.

Each statement is equivalent to

$AF \cdot FE = CF \cdot CF$ .

Divide both sides by $FE \cdot CF$ to yield a proportion statement:

$\frac{AF \cdot FE}{FE \cdot CF} = \frac{CF \cdot CF}{FE \cdot CF}$

$\frac{AF }{ CF} = \frac{CF }{FE }$

The sides of the rectangles are in proportion; subsequently, the rectangles are similar.

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Example Question #122 : Geometry

You are given two rectangles, $\textup{Rect } ABCD$ and $\textup{Rect } EFGH$

True or false: $\textup{Rect } ABCD \sim \textup{Rect } EFGH$ .

Statement 1: $AB \cdot FG= BC \cdot EF$

Statement 2: $AB \cdot GH= CD \cdot EF$

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.

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 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:

Assume Statement 1 alone. Divide both sides by $EF \cdot FG$ ,

$AB \cdot FG= BC \cdot EF$

$\frac{AB \cdot FG}{EF \cdot FG}= \frac{BC \cdot EF}{EF \cdot FG}$

$\frac{AB}{EF} = \frac{BC}{FG}$ .

This proportion statement asserts that sides of the two rectangles are in proportion. This is a necessary and sufficient condition for the rectangles to be similar.

Now examine Statement 2.

By the congruence of opposite sides of a rectangle,

AB = CD , GH = EF ,

and, regardless of whether the rectangles are similar or not,

$AB \cdot GH= CD \cdot EF$ .

Therefore, Statement 2 provides superfluous and unhelpful information.

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Example Question #123 : Geometry

You are given two rectangles, $\textup{Rect } ABCD$ and $\textup{Rect } EFGH$ .

Let the perimeter of $\textup{Rect } ABCD$ be , and let the perimeter of $\textup{Rect } EFGH$ be .

True or false: $\textup{Rect } ABCD \sim \textup{Rect } EFGH$ .

Statement 1: $\frac{AB}{EF} = \frac{p}{q}$

Statement 2: $\frac{AD}{EH} = \frac{p}{q}$

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 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.

BOTH statements TOGETHER are insufficient 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:

The perimeter of $\textup{Rect } ABCD$ is the sum of its sidelengths, and opposite sides are congruent, so

p = AB + BC + CD + AD

p = AB + BC + AB+ BC

$p = 2 \cdot AB + 2\cdot BC$

Similarly,

$q = 2 \cdot EF + 2 \cdot FG$

Therefore,

$\frac{p }{q}= \frac{2 \cdot AB + 2\cdot BC}{2 \cdot EF + 2 \cdot FG}$ ,

and, reducing,

$\frac{p }{q}= \frac{ AB + BC}{ EF + FG}$

Assume Statement 1 alone. Then

$\frac{p}{q} = \frac{AB}{EF}$ , or $\frac{p}{q} = \frac{-AB}{-EF}$ , and by a property of proportions,

$\frac{p }{q}= \frac{\left ( AB + BC \right )+(-AB)}{ \left (EF + FG \right )+(-EF)} = \frac{BC}{EF}$

Therefore,

$\frac{AB}{EF}= \frac{BC}{EF}$ ,

thereby proving the sides of the rectangles to be in proportion. As a consequence, $\textup{Rect } ABCD \sim \textup{Rect } EFGH$ .

By a similar argument, Statement 2 also proves $\textup{Rect } ABCD \sim \textup{Rect } EFGH$ .

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Example Question #4 : Dsq: Calculating Whether Rectangles Are Similar

You are given two rectangles, $\textup{Rect } ABCD$ and $\textup{Rect } EFGH$ .

Let the perimeter of $\textup{Rect } ABCD$ be , and let the perimeter of $\textup{Rect } EFGH$ be .

Let the area of $\textup{Rect } ABCD$ be and the area $\textup{Rect } EFGH$ be .

True or false: $\textup{Rect } ABCD \sim \textup{Rect } EFGH$ .

Statement 1: $\frac{p^{2}}{q^{2}} = \frac{r}{s}$

Statement 2: $\frac{AB}{EF} = \frac{p}{q}$

Possible Answers:

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.

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.

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.

Examine these three rectangles. The one of the left is $\textup{Rect } ABCD$ ; the other two have the same dimensions, and both are called $\textup{Rect } EFGH$ , except that the names of the vertices are differently arranged:

Rectangles

Regardless of which $\textup{Rect } EFGH$ is chosen, the ratio of the perimeters is $\frac{14}{28} = \frac{1}{2}$ and the ratio of the areas is $\frac{12}{48} = \frac{1}{4} =\left ( \frac{1 }{2} \right )^{2}$ . The conditions of the problem are met for both pairings, but in one case, $\textup{Rect } ABCD \sim \textup{Rect } EFGH$ and in the other, $\textup{Rect } ABCD \nsim \textup{Rect } EFGH$ (that is, the rectangles are similar, but the given similarity statement may or may not be true).

Assume Statement 2 alone.

The perimeter of $\textup{Rect } ABCD$ is the sum of its sidelengths, and opposite sides are congruent, so

p = AB + BC + CD + AD

p = AB + BC + AB+ BC

$p = 2 \cdot AB + 2\cdot BC$

Similarly,

$q = 2 \cdot EF + 2 \cdot FG$

Therefore,

$\frac{p }{q}= \frac{2 \cdot AB + 2\cdot BC}{2 \cdot EF + 2 \cdot FG}$ ,

and, reducing,

$\frac{p }{q}= \frac{ AB + BC}{ EF + FG}$

From Statement 2,

$\frac{p}{q} = \frac{AB}{EF}$ , or $\frac{p}{q} = \frac{-AB}{-EF}$ , and by a property of proportions,

$\frac{p }{q}= \frac{\left ( AB + BC \right )+(-AB)}{ \left (EF + FG \right )+(-EF)} = \frac{BC}{EF}$

Therefore,

$\frac{AB}{EF}= \frac{BC}{EF}$ ,

thereby proving the sides of the rectangles to be in proportion. As a consequence, $\textup{Rect } ABCD \sim \textup{Rect } EFGH$ .

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Example Question #1 : Dsq: Calculating Whether Rectangles Are Similar

You are given two rectangles, $\textup{Rect } ABCD$ and $\textup{Rect } EFGH$

True or false: $\textup{Rect } ABCD \sim \textup{Rect } EFGH$ .

Statement 1: $\frac{AC}{EG} = \frac{BD}{FH}$

Statement 2: $\frac{AB}{EF} = \frac{BC}{FG}$

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 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.

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 compares the lengths of the diagonals of the two rectangles. Since the diagonals of any rectangle are congruent, AC = BD , EG = FH , and, as a consequence, $\frac{AC}{EG} = \frac{BD}{FH}$ regardless of whether the rectangles are similar or not. Statement 1 is a superfluous statement and is therefore unhelpful.

Statement 2 asserts that sides of the two rectangles are in proportion. This is a necessary and sufficient condition for the rectangles to be similar.

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Example Question #2 : Dsq: Calculating Whether Rectangles Are Similar

You are given two rectangles, $\textup{Rect } ABCD$ and $\textup{Rect } EFGH$ .

Let the perimeter of $\textup{Rect } ABCD$ be , and let the perimeter of $\textup{Rect } EFGH$ be .

Let the area of $\textup{Rect } ABCD$ be and the area $\textup{Rect } EFGH$ be .

True or false: $\textup{Rect } ABCD \sim \textup{Rect } EFGH$ .

Statement 1: $\left (\frac{p }{q} \right ) ^{2}= \frac{r}{s}$

Statement 2: $\frac{AC}{EG} = \frac{p}{q}$

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:

BOTH statements TOGETHER are insufficient to answer the question.

Explanation:

Assume both statements to be true.

Rectangles

Regardless of which $\textup{Rect } EFGH$ is chosen:

The ratio of the perimeters is $\frac{14}{28} = \frac{1}{2}$ ;

The ratio of the areas is $\frac{12}{48} = \frac{1}{4} =\left ( \frac{1 }{2} \right )^{2}$ ; and,

The ratio $\frac{AC}{EG} = \frac{5}{10} = \frac{1}{2}$ .

The conditions of the problem are met for both pairings, but in one case, $\textup{Rect } ABCD \sim \textup{Rect } EFGH$ and in the other, $\textup{Rect } ABCD \nsim \textup{Rect } EFGH$ (that is, the rectangles are similar but the similarity statement given may be true or false).

The two statements together provide insufficient information.

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Example Question #1 : Dsq: Calculating The Perimeter Of A Polygon

Given a regular hexagon and a regular octagon, which, if either, has the greater perimeter?

Statement 1: The sidelength of the octagon is one foot.

Statement 2: The sidelength of the hexagon is fifteen inches.

Possible Answers:

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.

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:

Each of the two statements allows you to find out the perimeter of one of the polygons by multiplying its sidelength by the number of its sides. However, neither statement offers any clues to the perimeter of the other polygon. Both statements together, however, allow you to determine and to compare both perimeters.

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Example Question #1 : Polygons

You are given a regular hexagon and a regular pentagon. Which one has the greater perimeter?

Statement 1: The hexagon and the pentagon have the same area

Statement 2: The apothem of the hexagon is greater than that of the pentagon

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 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.

Correct answer:

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

Explanation:

The area of a polygon is one-half the product of its perimeter and its apothem (the perpendicular distance from the center to a side). Therefore,

$A = \frac{1}{2}ap$ ,

$\frac{1}{2}ap =A$

$\frac{1}{2}ap \cdot \frac{2}{a} =A\cdot \frac{2}{a}$

$p = \frac{2A}{a}$

Therefore, the perimeter can be determined from both area and apothem, but not from one alone. Neither statement alone gives you enough information, but from both statements together, it can be determined that the pentagon has the greater perimeter.

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Example Question #2 : Dsq: Calculating The Perimeter Of A Polygon

Untitled

Note: Figure NOT drawn to scale. All angles shown are right angles.

What is the perimeter of the above figure?

Statement 1: a = 20

Statement 2: b = 40

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.

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.

Correct answer:

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

Explanation:

The figure can be seen as a $d \times e$ rectangle cut out of an $a \times b$ rectangle.

Untitled

The perimeter of the composite figure is

P = a + b + c + d + e + f .

However, since opposite sides of a rectangle are congruent, then, as can be seen in the figure, c + e = b and d+f = a .

The perimeter can then be rewritten:

P = a + b + c + d + e + f

= a + d + f + b + c + e

= a + a + b + b

=2a + 2b

Therefore, it is necessary and sufficient to know and ; the other four sidelengths are not needed to determine the perimeter of the figure.

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GMAT Math : Data-Sufficiency Questions

Study concepts, example questions & explanations for GMAT Math

All GMAT Math Resources

Example Questions

Example Question #241 : Data Sufficiency Questions

Example Question #241 : Data Sufficiency Questions

Example Question #122 : Geometry

Example Question #123 : Geometry

Example Question #4 : Dsq: Calculating Whether Rectangles Are Similar

Example Question #1 : Dsq: Calculating Whether Rectangles Are Similar

Example Question #2 : Dsq: Calculating Whether Rectangles Are Similar

Example Question #1 : Dsq: Calculating The Perimeter Of A Polygon

Example Question #1 : Polygons

Example Question #2 : Dsq: Calculating The Perimeter Of A Polygon

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