All GMAT Math Resources
Example Questions
Example Question #2624 : Gmat Quantitative Reasoning
Given: and , where and are right angles.
True or false:
Statement 1: Both triangles are scalene.
Statement 2: The triangles have the same perimeter.
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.
BOTH statements TOGETHER are insufficient to answer the question.
Assume both statements are true. Consider these two scenarios:
Let
and
Since and , then by the Hypotenuse-Leg Theorem, , and it follows that .
Now, let
and .
The sides are not in proportion, as , so .
In both scenarios, since , the triangles are right by the converse of the Pythagorean Theorem, satisfying the main premise; the triangles are scalene, having sides of three different lengths, satisfying Statement 1; and the triangles both have perimeter , satisfying Statement 2. The two statements together are insufficient.
Example Question #2625 : Gmat Quantitative Reasoning
Given: and , where and are right angles.
True or false:
Statement 1: Both triangles are isosceles.
Statement 2: The triangles have the same perimeter.
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.
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.
Assume Statement 1 alone. By the 45-45-90 Theorem, an isosceles right triangle has two acute angles that each measure ; specifically, and . By the Angle-Angle Similarity Postulate, .
Assume Statement 2 alone. The equality of the perimeters of two right triangles does not imply their similarity or nonsimilarity. For example:
Let
and
Since and , it follows by the Hypotenuse-Leg Theorem that , and, since congruent triangles are similar, it further follows that .
Now, let
and .
The sides are not in proportion, as , so .
In both scenarios, since , by the converse of the Pythagorean Theorem, the triangles are right, and the triangles both have perimeter , thereby satisfying the main premise and Statement 2. Statement 2 alone is therefore insufficient.
Example Question #153 : Triangles
Given: Rectangles and with diagonals and , respectively.
True or false:
Statement 1: Rectangles and are both rhombuses.
Statement 2: Rectangles and are both squares.
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.
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.
EITHER statement ALONE is sufficient to answer the question.
Both rectangles, by definition, have four right angles.
A rhombus is a quadrilateral with four sides of equal length. A square is a quadrilateral with four right angles and four sides of equal length. Therefore, the two statements are actually equivalent in this context, so either they together provide insufficient information, or either alone does. We show that the latter is the case.
If both statements are true, and the rectangles are rhombuses and squares, then
and .
Consequently,
.
,
so by the Side-Angle-Side Similarity Theorem, .
Example Question #11 : Dsq: Calculating Whether Right Triangles Are Similar
Note: Figure NOT drawn to scale.
Refer to the above figure, which shows two right triangles circumscribed by circles.
True or false:
Statement 1: The area of the circle that circumscribes is four times the that of the circle that circumscribes .
Statement 2:
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.
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
Assume Statement 1 alone. The area of the circle that circumscribes is four times the that of the circle that circumscribes , so the radius of the former is the square root of this, or two, times the radius of the latter; therefore, the ratio of the diameters of the circles is also two. Since in a right triangle inscribed inside a circle, the hypotenuse must be a diameter of that circle,
or
However, no other information is given or can be determined about any other sides or angles, so the triangles cannot been proved or disproved to be similar.
Assume Statement 2 alone. , or , but again, no other information is given or can be determined about any other sides or angles, so the triangles have not been proved or disproved to be similar.
Now assume both statements. , setting up the conditions for the Hypotenuse-Leg Similarity Theorem; it follows that .
Example Question #51 : Right Triangles
Note: Figure NOT drawn to scale.
Refer to the above figure. True or false: .
Statement 1:
Statement 2:
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.
Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.
Assume Statement 1 alone. If , then corresponding angles are congruent - specifically, . Statement 1 directly contradicts this, so .
Statement 2 alone does not prove or disprove similarity, since information is only given about one set of corresponding sides. No information is given about corresponding angles, or any other set of corresponding sides.
Example Question #12 : Dsq: Calculating Whether Right Triangles Are Similar
Given: and , where and are right angles.
True or false:
Statement 1:
Statement 2:
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.
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.
Similarity of two triangles does not require that corresponding sides be congruent - only that they be in proportion. Therefore, the inequality of one pair of corresponding sides, as given in Statement 1 alone, is insufficient to prove or disprove that .
However, similarity of two triangles requires that all three pairs of corresponding angles be congruent. Therefore, Statement 2 alone, which establishes that one such pair is noncongruent, proves that .
Example Question #13 : Dsq: Calculating Whether Right Triangles Are Similar
Given: Rectangles and with diagonals and , respectively.
True or false:
Statement 1: Of the two rectangles, only Rectangle is a rhombus.
Statement 2:
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 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.
Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.
Assume Statement 1 alone. Rectangle is not a rhombus, so or . Rectangle is a rhombus, so . Therefore, either
or
Either way, the corresponding sides are not in proportion; it follows that .
Assume Statement 2 alone. No information is given about , so the quantities and cannot be proved to be equal or unequal. If they are unequal, since the sides are not in proportion, it follows that . If they are equal, then, since , it follows by the Side-Angle-Side similarity Theorem that .
Example Question #14 : Dsq: Calculating Whether Right Triangles Are Similar
Note: Figure NOT drawn to scale.
Refer to the above figure. True or false: .
Statement 1: Quadrilateral is a trapezoid.
Statement 2:
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.
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.
EITHER statement ALONE is sufficient to answer the question.
Assume Statement 1 alone. Since Quadrilateral is a trapezoid, it follows that ; by the Corresponding Angles Principle, . By reflexivity, . By the Angle-Angle Postulate, .
Assume Statement 2 alone.
Also, by reflexivity, . By the Side-Angle-Side Similarity Theorem, it follows that .
Example Question #15 : Dsq: Calculating Whether Right Triangles Are Similar
Note: Figure NOT drawn to scale.
Refer to the above diagram.
True or false:
Statement 1: Arcs and have the same degree measure.
Statement 2: Arcs and have the same degree measure.
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.
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.
EITHER statement ALONE is sufficient to answer the question.
Assume Statement 1 alone. and have the same degree measure, so the inscribed angles that intercept these arcs must also have the same degree measure - that is, . Since , both being right angles, this sets up the conditions of the Angle-Angle Postulate, so it follows that .
Assume Statement 2 alone. Major arc and major arc . by Statement 2, so
Again, the inscribed angles that intercept these arcs must also be congruent - that is, . Again, this, along with , prove that by way of the Angle-Angle Postulate.