All GMAT Math Resources
Example Questions
Example Question #9 : Dsq: Calculating The Height Of An Equilateral Triangle
Given and , with an equilateral triangle. Construct the altitude from to on , and the altitude from to on .
Which, if either, of and is longer?
Statement 1:
Statement 2: is a right angle.
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 sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
Assume both statements are true. From Statement 1 alone, , and , so and . Therefore, between and , two pairs of corresponding sides are congruent.
is an equilateral triangle, so ; from Statement 2, is a right angle, so . This means that the included angle in is of greater measure, so by the Side-Angle-Side Inequality Theorem, or Hinge Theorem, it has the longer opposite side, or . Both triangles are isosceles, so both altitudes divide the triangles into congruent right triangles, and by congruence, and are the midpoints of their respective sides. This means that
By the Pythagorean Theorem,
and
Since and ,
meaning that is the longer altitude.
Note that this depended on knowing both statements to be true. Statement 1 alone is insufficient, since, for example, had measured less than , then by the same reasoning, would have been the shorter altitude. Statement 2 alone is insufficient because it gives information only about one angle, and nothing about any side lengths.
Example Question #10 : Dsq: Calculating The Height Of An Equilateral Triangle
Given equilateral triangles and , construct the altitude from to on , and the altitude from to on .
True or false: or have the same length.
Statement 1: and are chords of the same circle.
Statement 2: and have the same area.
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.
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.
Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.
Statement 1 alone is inconclusive, since chords of the same circle can have different lengths.
Statement 2 alone is conclusive. The common side length of an equilateral triangle depends solely on the area, so it follows that the sides of two triangles of equal area will have the same common side length. Also, each altitude divides its triangle into two 30-60-90 triangles. Examining and , we can easily find that these triangles are congruent by way of the Angle-Side-Angle. Postulate, so it follows by triangle congruence that .
Example Question #331 : Geometry
Given equilateral triangles and , construct the altitude from to on , and the altitude from to on .
Which, if either, of and is longer?
Statement 1:
Statement 2:
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.
Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.
Let and be the common side lengths of and . The length of an altitude of a triangle is solely a function of its side length, so it follows that the triangle with the greater side length is the one whose altitude is the longer. Therefore, the question is equivalent to which, if either, of or is the greater.
Assume Statement 1 alone. This statement can be rewritten as
It follows that has the greater side length, and, consequently, that its altitude is longer than .
Assume Statement 2 alone. divides the triangle into two congruent triangles, so is the midpoint of ; therefore, . Statement 2 can be rewritten as
This statement is inconclusive. Suppose —that is, each side of is of length 1. Then , , and all make that inequality true; without further information, it is therefore unclear whether , the side length of , is less than, equal to, or greater than , the side length of . Consequently, it is not clear which triangle has the longer altitude.
Example Question #331 : Geometry
What is the perimeter of ?
(1) The area of the triangle is .
(2) is an equilateral triangle.
Each statement alone is sufficient
Statement 2 alone is sufficient
Statement 1 alone is sufficient
Statements 1 and 2 taken together are not sufficient
Both statements together are sufficient
Both statements together are sufficient
To find the perimeter we should be able to calculate each sides of the triangle.
Statement 1 tells us the area of the triangle. From this we can't calculate anything else, since we don't know whether the triangle is of a special type.
Statement 2 tells us that the triangle is equilateral. Again This information alone is not sufficient.
Taken together these statements allow us to find the sides of the equilateral triangle ABC. Indeed, the area of an equilateral triangle is given by the following formula: . Where is the area and the length of the side.
Therefore both statements are sufficient.
Example Question #2 : Dsq: Calculating The Perimeter Of An Equilateral Triangle
Find the perimeter of given the following:
I) .
II) Side .
Both statements are needed to answer the question.
Neither statement is sufficient to answer the question. More information is needed.
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.
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.
To find perimeter, we need the side lengths.
I) Gives us the measure of two angles. The given measurement is equal to 60 degrees. This means the last angle is also 60 degrees.
II) Gives us one side length, but because we know from I) that this is an equilateral triangle, we know that all the sides have the same length.
Add up all the sides to get the perimeter.
We need I) and II) to find the perimeter
Example Question #1 : Dsq: Calculating The Perimeter Of An Equilateral Triangle
Given two equilateral triangles and , which, if either, has the greater perimeter?
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.
EITHER statement ALONE is sufficient to answer the question.
The area of an equilateral triangle is given by the formula
,
where is its common sidelength. It follows that the triangle with the greater sidelength has the greater area.
We will let and stand for the common sidelength of and , respectively. The question becomes which, if either, of and is the greater.
Statement 1 alone can be rewritten by multiplying:
Therefore, .
Therefore, , the length of one side of is less than , the length of one side of .
Statement 2 alone can be rewritten as . Again, it follows that .
From either statement alone, it follows that . has the greater sidelength, and, consequently, the greater area.
Example Question #451 : Data Sufficiency Questions
Given two equilateral triangles and , which, if either, has the greater perimeter?
Statement 1:
Statement 2: has greater area than .
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.
EITHER statement ALONE is sufficient to answer the question.
Since an equilateral triangle has three sides of equal measure, the perimeter of an equilateral triangle is three times its sidelength, so the triangle with the greater common sidelength has the greater perimeter.
Statement 1 gives precisely this information; since one side of is longer than one side of , it follows that has the longer perimeter.
Statement 2 gives that has the greater area. Since the area of an equilateral triangle depends only on the common length of its sides, the triangle with the greater area, , must also have the greater sidelength and, consequently, the greater perimeter.
Example Question #5 : Dsq: Calculating The Perimeter Of An Equilateral Triangle
Give the perimeter of equilateral triangle .
Statement 1: is a radius of a circle with area .
Statement 2: is the hypotenuse of a 30-60-90 triangle with area .
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. To find the radius of a circle with area , use the area formula:
This is also the length of each side of , so its perimeter is three times this, or 24.
Assume Statement 2 alone. If we let be the length of , then, since this the hypotenuse of a 30-60-90 triangle, by the 30-60-90 Theorem, the legs measure and . Half the product of their lengths is equal to area , so
.
As before, the sidelength of is 8 and the perimeter is 24.
Example Question #92 : Triangles
Given two equilateral triangles and , which has the greater perimeter?
Statement 1: is the midpoint of .
Statement 2: is the midpoint 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.
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.
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
Neither statement alone is enough to determine which triangle has the greater perimeter, as each statement gives information about only one point.
Assume both statements to be true. Since is the segment that connects the endpoints of two sides of , it is a midsegment of the triangle, whose length is half the length of the side of to which it is parallel. Therefore, the sidelength of is half that of , and their perimeters are similarly related. This makes the triangle with the greater perimeter.
Example Question #7 : Dsq: Calculating The Perimeter Of An Equilateral Triangle
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.
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.
EITHER statement ALONE is sufficient to answer the question.
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.
If we let and be the common sidelengths of and , respectively, Statement 1 can be rewritten as the equation . This can be expressed as follows:
Therefore, .
Statement 2 can be rewritten as
Once again,
Since either statement alone establishes that , it follows that has the longer sides and, consequently, the greater perimeter of the triangles.