All GMAT Math Resources
Example Questions
Example Question #171 : Geometry
Note: Figure NOT drawn to scale.
Refer to the above figure, which shows a tetrahedron, or triangular pyramid. What is the volume of the tetrahedron?
Statement 1: is an isosceles triangle with area 64.
Statement 2: is an equilateral triangle with perimeter 48.
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.
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
Each statement gives enough information about one triangle to determine its area, its angles, and its sidelengths, but no information about the other three triangles is given except for one side.
Assume both statements are known. is an isosceles triangle with area 64. Since , we can find this common sidelength using the area formula for a triangle, with these lengths as height and base:
.
This is the length of both and .
By the 45-45-90 Theorem, has length times this, or .
Since is an equilateral triangle, . Since is a right triangle, , and , the triangle is also isosceles, and ; by a similar argument, .
The volume of the pyramid can be calculated. Its base, which is congruent to , has area 64, and its height is ; multiply one third by their product to get the volume.
Example Question #172 : Geometry
Pyramid 1 in three-dimensional coordinate space has as its base the square with vertices at the origin, , , and , and its apex at the point ; Pyramid 2 has as its base the square with vertices at the origin, , , and , and its apex at the point . All six variables represent positive quantities. Which pyramid has the greater volume?
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.
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 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.
The volume of a pyramid is one third the product of its height and the area its base.
Pyramid 1 is shown below:
The base of the pyramid is on the -plane, so the height of the pyramid is the perpendicular distance from apex to this plane; this is the -coordinate, . The base of the pyramid is a square of sidelength 10, so its area is the square of 10, or 100. This makes the volume of Pyramid 1
Similarly, the volume of Pyramid 2 is
The problem therefore asks us which, if either, of to is the greater quantity.
Assume Statement 1 alone. If , then , and
Since , it follows that , and - that is, Pyramid 2 has the greater volume.
Statement 2 alone gives insufficient information. We take two sets of values of and that add up to 25:
Case 1:
In this case, Pyramid 2 has the greater height and the greater base area, so it easily follows that Pyramid 2 has the greater volume.
Case 2:
Then the volume of Pyramid 1 is
and that of Pyramid 2 is
This makes Pyramid 1 the greater in volume.
Example Question #7 : Dsq: Calculating The Volume Of A Tetrahedron
Note: Figure NOT drawn to scale, but you may assume .
In the above figure, a pyramid with a rectangular base is inscribed inside a rectangular prism; its vertices are . What is the volume of the pyramid?
Statement 1: The hypotenuse of 30-60-90 triangle has length 16.
Statement 2: The hypotenuse of 45-45-90 right triangle has length .
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.
The volume of the pyramid is one third the product of height and the area of its rectangular base, which is ; that is,
Assume Statement 1 alone. is a 30-60-90 triangle with a hypotenuse of length 16. By the 30-60-90 Triangle Theorem, short leg has length half this, or 8, and long leg has length times that of , or . However, the length of cannot be determined.
Assume Statement 2 alone. is a 45-45-90 right triangle with a hypotenuse of length . By the 45-45-90 Theorem, its legs and each have length divided by , which is ; however, the length of cannot be determined.
From the two statements together, we can determine that and , and calculate the volume:
.
Example Question #8 : Dsq: Calculating The Volume Of A Tetrahedron
Note: Figure NOT drawn to scale.
The above figure shows a rectangular prism with an inscribed tetrahedron, or triangular pyramid, with vertices . What is the volume of the tetrahedron?
Statement 1: Isosceles right triangle has area 32.
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.
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 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.
The volume of the pyramid is one third the product of the height, which is , and the area of the base; this base, being a right triangle, is equal to one half the product of the lengths of its legs, or and . Therefore,
or
From Statement 1 alone, we know is isosceles and has area 32; therefore, its common leg length can be determined using the area formula:
Therefore, . However, nothing can be determined about .
Statement 2 alone does not give any of the three desired lengths or any information necessary to find them.
However, Statement 2, along with the information from Statement 1, can be used to find . From Statement 2, , and from Statement 1, ; the Pythagorean Theorem can be used to find . Therefore, all three of , , and can be found, and the volume of the pyramid can be calculated.
Example Question #2 : Rectangular Solids & Cylinders
A regular tetrahedron is a solid with four faces, each of which is an equilateral triangle.
Give the volume of a regular tetrahedron.
Statement 1: Each edge has length 8.
Statement 2: Each face has area .
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.
BOTH statements TOGETHER are insufficient to answer the question.
EITHER statement ALONE is sufficient to answer the question.
The formula for the volume of a regular tetrahedron given the length of each edge is
.
Statement 1 gives information explicitly. Statement 2 gives the means to find , since, if is substituted for in the formula for an equilateral triangle:
,
the value of can be determined.
Example Question #11 : Tetrahedrons
Note: Figure NOT drawn to scale.
The above figure shows a rectangular prism with an inscribed tetrahedron, or triangular pyramid, with vertices . What is the volume of the tetrahedron?
Statement 1: Rectangle has area 200.
Statement 2: Rectangle has area 120.
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.
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.
The volume of the pyramid is one third the product of the height, which is , and the area of the base; this base, being a right triangle, is equal to one half the product of the lengths of its legs, or and . Therefore,
or
We need to know the values of , , and to find the volume of of the pyramid. We show that the two statements give insufficient information by examining two scenarios.
Case 1:
Rectangle has area .
Rectangle has area .
The volume of the pyramid is
Case 2:
Rectangle has area .
Rectangle has area .
The volume of the pyramid is
In each case, the conditions of both statements are met, but the volumes of the pyramids differ.
Example Question #291 : Data Sufficiency Questions
The above figure shows a cube; a pyramid with vertices at is inscribed. What is the volume of the pyramid?
Statement 1: The cube has volume 729.
Statement 2: has area .
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 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.
Let be the common length of the edges of the cube.
The height of the pyramid is , and the area of its base, Square , is . The volume of the pyramid is one third the product of these, or
Therefore, if the common length of the edges of the cube can be found, the volume of the pyramid can be calculated.
From Statement 1 alone, this length can be calculated as the cube root of the volume of the cube, 729; this cube root is equal to 9.
From Statement 2 alone, this length can also be calculated. has as one leg with length ; its other leg, which is a diagonal of a square with sidelength has length by the 45-45-90 Theorem. The area is half the product of these legs; since this area is , we can find as follows:
From either statement alone, can be calculated to be 9, and the volume of the pyramid can be found to be
Example Question #292 : Data Sufficiency Questions
A regular tetrahedron has four equilateral faces and six congruent edges.
Of a given regular tetrahedron and a given right regular square pyramid, which, if either, has the greater volume?
Statement 1: The length of each side of the base of the square pyramid has the same length as one edge of the tetrahedron.
Statement 2: The height of the square pyramid has the same length of one edge of the tetrahedron.
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 insufficient 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 sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
Let be the length of one edge of the regular tetrahedron. Its volume can be calculated using the formula
.
Now let be the length of each side of the square base of the square pyramis, and be the height of the square pyramid. Since the volume of this pyramid is one third the product of the height and the area of the base, the volume can be calculated using the formula
, or
Statement 1 alone tells us that , allowing the formula to be rewritten
,
but with no information about the height, we cannot compare this to tetrahedron height .
Likewise,
Statement 1 alone tells us that , allowing the formula to be rewritten
,
but with no information about the sidelength or area of the base, we cannot compare this to the tetrahedron height.
Now assume both statements to be true. We know that , so the formula for the square pyramid is
Since , it follows that:
and the square pyramid has the greater volume.
Example Question #2401 : Gmat Quantitative Reasoning
A tetrahedron is a solid with four triangular faces.
Give the volume of a tetrahedron.
Statement 1: The tetrahedron has four equilateral faces.
Statement 2: The surface area of the tetrahedron is .
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.
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.
BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.
Neither statement is enough to determine the volume of the tetrahedron; Statement 1 alone gives no actual measurements, and Statement 2 gives only the surface area, which can apply to infinitely many tetrahedrons.
Assume both statements to be true. A tetrahedron with four equilateral faces is a regular tetrahedron, whose surface area, relative to the common length of its edges, is defined by the formula
.
By substituting for , it is possible to calculate . Consequently, the volume of the tetrahedron can be calculated using the volume formula
.
Example Question #294 : Data Sufficiency Questions
Note: Figure NOT drawn to scale.
The above figure shows a rectangular prism with an inscribed tetrahedron, or triangular pyramid, with vertices . What is the volume of the tetrahedron?
Statement 1: Rectangle has area 240.
Statement 2: Square has area 144.
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.
The volume of the pyramid is one third the product of the height, which is , and the area of the base; this base, being a right triangle, is equal to one half the product of the lengths of its legs, or and . Therefore,
or
From Statement 1, it can be determined that , but without knowing anything about , the volume of the pyramid cannot be determined. Similarly, from Statement 2, it can be determined that , but nothing is given about .
Now assume both statements are true. Statement 2 gives that Quadrilateral is a square with area 144, so . From Statement 1, we can tell . The volume of the pyramid can be calculated as
.