All GMAT Math Resources
Example Questions
Example Question #101 : Triangles
Which, if either, of equilateral triangles and , has the greater perimeter?
Statement 1:
Statement 2:
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.
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.
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
If we let and be the sidelengths of and , respectively; the statements can be rewritten as:
Statement 1:
Statement 2:
Since the perimeter of an equilateral triangle is three times its common sidelength, comparison of the lengths of the sides is all that is necessary to determine which triangle, has the greater perimeter. The question can therefore be reduced to asking which of and , if either, is greater.
Statement 1 alone is not sufficient to yield an answer:
Case 1:
Case 2:
Both cases satisfy Statement 1, but in the first case, , meaning that has greater sidelength and perimeter than , and in the second case, , meaning the reverse. By a similar argument, Statement 2 is insufficient.
Now assume both statements to be true. The two equations together comprise a system of equations:
Multiply the first equation by 3 and the second by , then add:
Now substitute back:
has the greater sidelength and, consequently, the greater perimeter.
Example Question #102 : Triangles
Given an equilateral triangle and a right triangle with right angle , which has the greater perimeter?
Statement 1:
Statement 2:
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.
Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.
Assume Statement 1 alone. Since in , is the right angle, is the hypotenuse, which is longer than either of the two legs - and . Since, in equilateral triangle , , it follows that and . Consequently
,
and has the greater perimeter.
Statement 2 alone gives insufficient information, since we know nothing about the second leg or the hypotenuse of . We see this by examining these two cases.
Case 1: Let be an equilateral triangle of sidelength 6, and in . If second leg of has length 4, then the triangle is a 3-4-5 triangle, with hypotenuse having length 5. The perimeter of is , and the perimeter of is . has the greater perimeter.
Case 2: Let be an equilateral triangle of sidelength 6, and in . If second leg of has length 20, has the greater perimeter on the basis of one side alone.
Example Question #103 : Triangles
Find the perimeter of the equilateral triangle.
- A side measures .
- The area is .
Statements 1 and 2 are not sufficient, and additional data is needed to answer the question.
Statement 2 alone is sufficient, but statement 1 alone is not sufficient 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.
Each statement alone is sufficient to answer the question.
Recall the formula for perimeter of a triangle.
where represents the side length of the triangle
Statement 1: We're given the length of the side so all we need to do is plug this value into the equation.
Statement 2: We're given the area so we first need to solve for the side length.
Now we can plug the value into the equation, like we did in Statement 1.
Example Question #1 : Right Triangles
Note: Figure NOT drawn to scale.
Refer to the above diagram.
True or false:
Statement 1: is an altitude of
Statement 2: bisects
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.
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 sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
To prove triangle congruence, we need to establish some conditions involving side and angle congruence.
We know from reflexivity.
If we only assume Statement 1, then we know that , both angles being right angles. If we only assume Statement 2, then we know that by definition of a bisector. Either way, we only have one angle congruence and one side congruence, not enough to establish congruence between triangles. The two statements together, however, set up the Angle-Side-Angle condition, which does prove that .
Example Question #2 : Right Triangles
Note: Figure NOT drawn to scale.
Refer to the above diagram.
True or false:
Statement 1: is the perpendicular bisector of .
Statement 2: is the bisector of .
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.
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 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.
To prove triangle congruence, we need to establish some conditions involving side and angle congruence.
We know from reflexivity.
From Statement 1 alone, by definition, and, since both and are right angles, . This sets the conditions to apply the Side-Angle-Side Postulate to prove that .
From Statement 2 alone,we know that by definition of a bisector. But we only have one angle congruence and one side congruence, not enough to establish congruence between triangles.
Example Question #3 : Right Triangles
Given: and , with right angles
True or false: .
Statement 1:
Statement 2:
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.
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 sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
Assume Statement 1 alone. If , then and . That does not prove or disprove the congruence statement. Therefore, Statement 1 alone - and by a similar argument, Statement 2 alone - is not sufficient to answer the question.
Now assume both statements to be true.
Suppose . Then this, along with the two statements, can be combined to yield the statement
.
Similarly, if ,
,
and .
and cannot both be true, so it is impossible for .
Example Question #4 : Right Triangles
Given: and , with right angles
True or false: .
Statement 1:
Statement 2:
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.
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.
From Statement 1 alone, we are only give one angle congruency and one side congruency, which, without further information, is not enough to prove or to disprove triangle congruence. By a similar argument, Statement 2 alone is not sufficient either.
Assume both statements are true. By Statement 1, the hypotenuses are congruent, and by Statement 2, one pair of corresponding legs are congruent. These are the conditions of the Hypotenuse Leg Theorem, so is proved to be true.
Example Question #5 : Dsq: Calculating Whether Right Triangles Are Congruent
Given: and , with right angles
True or false: .
Statement 1:
Statement 2:
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.
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.
Each statement alone give information about only one of the triangles; without information about the other triangle, it is impossible to prove or to disprove triangle congruence.
Assume both statements are true. For , it must hold that both and . If , then since , then , and since , then . Therefore, . Similarly, if , then , and ; again, . Therefore, the two statements together prove that is false.
Example Question #3 : Dsq: Calculating Whether Right Triangles Are Congruent
Given: and , with right angles
True or false: .
Statement 1: and .
Statement 2:
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.
EITHER statement ALONE is sufficient to answer the question.
BOTH statements TOGETHER are insufficient to answer the question.
Assume both statements to be true.
and , so hypotenuse can be calculated using the Pythagorean Theorem:
This establishes that - that is, that the hypotenuses of triangles are congruent. This gives us one side congruence and one angle congruence, the right angles, between the triangles; however, we are not given any other side or angle congruences, so we cannot determine whether or not the triangles are congruent.
Example Question #4 : Dsq: Calculating Whether Right Triangles Are Congruent
Given: and , with right angles
True or false: .
Statement 1:
Statement 2:
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 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.
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
Assume Statement 1 only. By the Pythagorean Theorem, , so ; subsequently, , and one side congruence is proved. However, this, along with one angle congruence - the congruence of right angles and - is not enough to prove or disprove triangle congruence.
Assume Statement 2 only. By the Pythagorean Theorem, , so ; subsequently, , and one side congruence is proved. For the same reason as with Statement 1, this provides insufficient information.
The two statements together, however, are sufficient. Statements 1 and 2 estabish congruence between the hypotenuses and corresponding legs, respectively, setting up the conditions of the Hypotenuse-Leg Theorem. As a consequence, .