GMAT Math : Rectangles

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #81 : Quadrilaterals

Farmer Jeff Jenkins is making a new rectangular field for his goats and needs to know how much fencing he needs to buy.

I) The goats will need at least \(\displaystyle 640\) square yards to roam.

II) One edge of the field will be \(\displaystyle 40\) yards long and will be made up of a river.

Possible Answers:

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

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

Either statement is sufficient to answer the question.

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

Both statements are needed to answer the question.

Correct answer:

Both statements are needed to answer the question.

Explanation:

To find perimeter, we need the lengths of both sides.

I) Gives us the area, which gives us one equation and two unknowns. Alone this statement is not sufficient.

II) Gives us one side length of the field.

We can use this with I) to find the other side length.

Once we have both sides, we can find perimeter easily.

\(\displaystyle A=bh \rightarrow 640=40h\)

\(\displaystyle h=16\)

Thus the perimeter is,

\(\displaystyle P=2b+2h \rightarrow P=2(40)+2(16)=112\).

Example Question #82 : Quadrilaterals

What is the perimeter of the rectangle?

  1. The area is \(\displaystyle 12in^2\).
  2. The width measures \(\displaystyle 6 in\).
Possible Answers:

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

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

Each statement alone is sufficient to answer the question.

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

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

Correct answer:

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

Explanation:

Statement 1: Although the area is given, we need more information in order to answer the question.

 \(\displaystyle l\times w=12\) but this can means our dimenions are \(\displaystyle 6 \times 2\) or \(\displaystyle 4 \times 3\)

Statement 2: We're told the width measures \(\displaystyle 6\) which means our dimensions are \(\displaystyle 6\times 2\)

Using BOTH statements, we can find the perimeter: \(\displaystyle 2(l+w)=2(2+6)=16\)

Example Question #83 : Quadrilaterals

True or false: \(\displaystyle A+ B > 50\)

Statement 1: A rectangle with length \(\displaystyle A\) and width \(\displaystyle B\) has area greater than 100.

Statement 2: A rectangle with length \(\displaystyle A\) and width \(\displaystyle B\) has perimeter greater than 100.

Possible Answers:

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

EITHER STATEMENT ALONE provides 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.

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.

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: \(\displaystyle A = 10, B = 12\)

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

\(\displaystyle A + B = 10+12 = 22 < 50\)

Case 2: \(\displaystyle A =40, B = 12\)

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

\(\displaystyle A + B = 40+12 = 52 > 50\)

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

\(\displaystyle 2(A+B)> 100\)

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

\(\displaystyle A + B > 50\), answering the question in the affirmative.

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:\(\displaystyle \textup{Rect } ABCF \sim \textup{Rect } CDEF\).

Statement 1:  \(\displaystyle CF = \sqrt{AF \cdot FE}\)

Statement 2: \(\displaystyle AF \cdot FE = AB \cdot DE\)

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.

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:

EITHER statement ALONE is sufficient to answer the question.

Explanation:

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

Each statement is equivalent to

\(\displaystyle AF \cdot FE = CF \cdot CF\).

Divide both sides by \(\displaystyle FE \cdot CF\) to yield a proportion statement:

\(\displaystyle \frac{AF \cdot FE}{FE \cdot CF} = \frac{CF \cdot CF}{FE \cdot CF}\)

\(\displaystyle \frac{AF }{ CF} = \frac{CF }{FE }\)

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

Example Question #242 : Data Sufficiency Questions

You are given two rectangles, \(\displaystyle \textup{Rect } ABCD\) and \(\displaystyle \textup{Rect } EFGH\)

True or false: \(\displaystyle \textup{Rect } ABCD \sim \textup{Rect } EFGH\).

Statement 1: \(\displaystyle AB \cdot FG= BC \cdot EF\) 

Statement 2: \(\displaystyle AB \cdot GH= CD \cdot EF\)

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 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.

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. Divide both sides by \(\displaystyle EF \cdot FG\),

\(\displaystyle AB \cdot FG= BC \cdot EF\)

\(\displaystyle \frac{AB \cdot FG}{EF \cdot FG}= \frac{BC \cdot EF}{EF \cdot FG}\)

\(\displaystyle \frac{AB}{EF} = \frac{BC}{FG}\)

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, 

\(\displaystyle AB = CD\)\(\displaystyle GH = EF\)

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

\(\displaystyle AB \cdot GH= CD \cdot EF\).

Therefore, Statement 2 provides superfluous and unhelpful information.

Example Question #22 : Rectangles

You are given two rectangles, \(\displaystyle \textup{Rect } ABCD\) and \(\displaystyle \textup{Rect } EFGH\).

Let the perimeter of \(\displaystyle \textup{Rect } ABCD\) be \(\displaystyle p\), and let the perimeter of \(\displaystyle \textup{Rect } EFGH\) be \(\displaystyle q\).

True or false: \(\displaystyle \textup{Rect } ABCD \sim \textup{Rect } EFGH\).

Statement 1: \(\displaystyle \frac{AB}{EF} = \frac{p}{q}\)

Statement 2: \(\displaystyle \frac{AD}{EH} = \frac{p}{q}\)

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:

EITHER statement ALONE is sufficient to answer the question.

Explanation:

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

\(\displaystyle p = AB + BC + CD + AD\)

\(\displaystyle p = AB + BC + AB+ BC\)

\(\displaystyle p = 2 \cdot AB + 2\cdot BC\)

Similarly,

\(\displaystyle q = 2 \cdot EF + 2 \cdot FG\)

Therefore, 

\(\displaystyle \frac{p }{q}= \frac{2 \cdot AB + 2\cdot BC}{2 \cdot EF + 2 \cdot FG}\),

and, reducing,

\(\displaystyle \frac{p }{q}= \frac{ AB + BC}{ EF + FG}\)

Assume Statement 1 alone. Then 

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

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

Therefore, 

\(\displaystyle \frac{AB}{EF}= \frac{BC}{EF}\),

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

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

Example Question #23 : Rectangles

You are given two rectangles, \(\displaystyle \textup{Rect } ABCD\) and \(\displaystyle \textup{Rect } EFGH\).

Let the perimeter of \(\displaystyle \textup{Rect } ABCD\) be \(\displaystyle p\), and let the perimeter of \(\displaystyle \textup{Rect } EFGH\) be \(\displaystyle q\).

Let the area of \(\displaystyle \textup{Rect } ABCD\) be \(\displaystyle r\) and the area \(\displaystyle \textup{Rect } EFGH\) be \(\displaystyle s\).

True or false: \(\displaystyle \textup{Rect } ABCD \sim \textup{Rect } EFGH\).

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

Statement 2: \(\displaystyle \frac{AB}{EF} = \frac{p}{q}\)

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:

Assume Statement 1 alone. 

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

Rectangles

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

Assume Statement 2 alone. 

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

\(\displaystyle p = AB + BC + CD + AD\)

\(\displaystyle p = AB + BC + AB+ BC\)

\(\displaystyle p = 2 \cdot AB + 2\cdot BC\)

Similarly,

\(\displaystyle q = 2 \cdot EF + 2 \cdot FG\)

Therefore, 

\(\displaystyle \frac{p }{q}= \frac{2 \cdot AB + 2\cdot BC}{2 \cdot EF + 2 \cdot FG}\),

and, reducing,

\(\displaystyle \frac{p }{q}= \frac{ AB + BC}{ EF + FG}\)

From Statement 2,

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

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

Therefore, 

\(\displaystyle \frac{AB}{EF}= \frac{BC}{EF}\),

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

Example Question #241 : Data Sufficiency Questions

You are given two rectangles, \(\displaystyle \textup{Rect } ABCD\) and \(\displaystyle \textup{Rect } EFGH\)

True or false: \(\displaystyle \textup{Rect } ABCD \sim \textup{Rect } EFGH\).

Statement 1: \(\displaystyle \frac{AC}{EG} = \frac{BD}{FH}\)

Statement 2: \(\displaystyle \frac{AB}{EF} = \frac{BC}{FG}\)

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:

Statement 1 compares the lengths of the diagonals of the two rectangles. Since the diagonals of any rectangle are congruent, \(\displaystyle AC = BD\)\(\displaystyle EG = FH\), and, as a consequence, \(\displaystyle \frac{AC}{EG} = \frac{BD}{FH}\) 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. 

Example Question #89 : Quadrilaterals

You are given two rectangles, \(\displaystyle \textup{Rect } ABCD\) and \(\displaystyle \textup{Rect } EFGH\).

Let the perimeter of \(\displaystyle \textup{Rect } ABCD\) be \(\displaystyle p\), and let the perimeter of \(\displaystyle \textup{Rect } EFGH\) be \(\displaystyle q\).

Let the area of \(\displaystyle \textup{Rect } ABCD\) be \(\displaystyle r\) and the area \(\displaystyle \textup{Rect } EFGH\) be \(\displaystyle s\).

True or false: \(\displaystyle \textup{Rect } ABCD \sim \textup{Rect } EFGH\).

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

Statement 2: \(\displaystyle \frac{AC}{EG} = \frac{p}{q}\)

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.

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.

Correct answer:

BOTH statements TOGETHER are insufficient to answer the question. 

Explanation:

Assume both statements to be true.

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

Rectangles

Regardless of which \(\displaystyle \textup{Rect } EFGH\) is chosen:

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

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

The ratio \(\displaystyle \frac{AC}{EG} = \frac{5}{10} = \frac{1}{2}\).

The conditions of the problem are met for both pairings, but in one case, \(\displaystyle \textup{Rect } ABCD \sim \textup{Rect } EFGH\) and in the other, \(\displaystyle \textup{Rect } ABCD \nsim \textup{Rect } EFGH\) (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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