GMAT Math : Data-Sufficiency Questions

Study concepts, example questions & explanations for GMAT Math

varsity tutors app store varsity tutors android store

Example Questions

Example Question #32 : Polygons

What is the area of a regular hexagon?

Statement 1: The area of the circle inscribed inside the hexagon is .

Statement 2: The circumference of the circle that is circumscribed about the hexagon is .

Possible Answers:

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.

Correct answer:

EITHER statement ALONE is sufficient to answer the question.

Explanation:

A regular hexagon can be viewed as a composite of six equilateral triangles, each of whose sidelength is the radius - the distance from its center to a vertex - of the hexagon. If the radius of the hexagon  is known, then the area of the hexagon can be calculated to be .

From Statement 1 alone, the radius of the inscribed circle, or incircle, can be calculated from the area formula (by dividing the area by  and extracting the square root). This length coincides with the height of each equilateral triangle. From there, the 30-60-90 Theorem can be used to find the sidelength of each triangle, and the area of the hexagon follows.

From Statement 2 alone, the radius of the circumscribed circle, or circumcircle, can be found by dividing its circumference by . This radius coincides with the radius of the hexagon, and the area can be calculated from there.

Example Question #2 : Dsq: Calculating The Area Of A Polygon

Octagon_1

Give the area of the above regular octagon.

Statement 1: The circle that circumscribes Quadrilateral  has area .

Statement 2:  has area 16.

Possible Answers:

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.

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:

Quadrilateral  is a square; each of its diagonals is a diameter of its circumscribed circle, or circumcircle. Therefore, if we know the area of its circumcircle from Statement 1 to be , we can calculate the radius from the area formula (divide by , extract the square root of the quotient). Twice this is the diameter, which is also the length of a diagonal of this square. Divide this by  to get . This is also equal to , the length of one side; this is sufficient to get the area of the octagon. 

From Statement 2 alone, since the area of isosceles triangle  is known to be 8, the length of each leg can be found using the formula

Since  is a 45-45-90 triangle, multiply this leg length by  to get , the length of one side; this is sufficient to get the area of the octagon. 

Example Question #1 : Rectangular Solids & Cylinders

Find the length of the edge of a tetrahedron.

Statement 1: The volume is 6.

Statement 2: The surface area is 6.

Possible Answers:

Correct answer:

Explanation:

Statement 1:) The volume is 6.

Write the formula to find the edge of the tetrahedron given the volume.

Given the volume, it is possible to find the edge of the tetrahedron.

Statement 2:) The surface area is 6.

Write the formula to find the edge of the tetrahedron given the surface.

Substitute the surface area to find the edge.

Therefore:

Example Question #1 : Dsq: Calculating The Volume Of A Tetrahedron

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:   and 

Statement 2:   

Possible Answers:

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.

Correct answer:

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Explanation:

The volume of a pyramid is one third the product of its height and the area its base. The two pyramids have the same base, so the pyramid with the greater height will have the greater volume (and if their heights are equal, their volumes are equal).

Pyramid 1 is shown below:

Pyramid

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

Therefore, the problem asks us to determine which of  and  is the greater.

Assume Statement 1 alone. Since , we can multiply all expressions by  to get a range for the volume of Pyramid 1:

Similarly, since , we can multiply all expressions by 36 to get a range of values for the volume of Pyramid 2:

Since the two ranges share values, it cannot be determined for certain which pyramid has the greater volume.

Assume Statement 2 alone. Then, since  and  , it easily follows that 

,

and, subsequently, Pyramid 2 has the greater volume.

Example Question #2 : Dsq: Calculating The Volume Of A Tetrahedron

Pyramid_2

Note: Figure NOT drawn to scale, but you may assume  and .

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: 30-60-90 triangle  has area .

Statement 2: Isosceles right triangle  has area 50.

Possible Answers:

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.

Statement 2 ALONE is sufficient to answer the question, but Statement 1 ALONE is NOT sufficient to answer the question.

Correct answer:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Explanation:

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.   has area , which is half the product of the length of shorter leg  and longer leg . Also, by the 30-60-90 Theorem, , so, combining these statements,

, and 

However, we do not have any way of finding out , so the volume cannot be calculated.

Assume Statement 2 alone.  is isosceles, so ; again, since the area of a right triangle is half the product of the lengths of its legs, 

However, we have no way of finding out .

The two statements together give all three of , and , so the volume can be calculated as 

Example Question #1 : Tetrahedrons

A solid in three-dimensional coordinate space has four vertices, at points , and  for some positive values of  . What is the volume of the solid?

Statement 1: 

Statement 2: 

Possible Answers:

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.

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:

 

The figure described is the triangular pyramid, or tetrahedron, in the coordinate three-space below.

Tetrahedron

The base of the pyramid can be seen as a triangle with the three known coordinates , and , and the area of its base is half the product of the lengths of its legs, which is 

.

The volume of the pyramid is one third the product of the area of its base, which is 48, and its height, which is the perpendicular distance from the unknown point to the base. Since the base is entirely within the -plane, this distance is the -coordinate of the apex, which is . Therefore, the only thing that is needed to determine the volume of the pyramid is ; this information is provided in Statement 2, but not Statement 1.

Example Question #1 : Tetrahedrons

Tetra_1

In the above diagram, a tetrahedron - a triangular pyramid - with vertices  is shown inside a cube. Give the volume of the tetrahedron.

Statement 1: The perimeter of Square  is 16.

Statement 2: The area of  is 8.

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 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.

Correct answer:

EITHER statement ALONE is sufficient to answer the question.

Explanation:

The volume of the pyramid is one third the product of height  and the area of its base, which in turn, since here it is a right triangle, is half the product of the lengths  and  of its legs. Since the prism in the figure is a cube, the three lengths are equal, so we can set each to . The volume of the pyramid is

Therefore, knowing the length of one edge of the cube is sufficient to determine the volume of the pyramid.

Assume Statement 1 alone. Since the perimeter of Square  is 16, each side of the square, and each edge of the cube has one fourth this measure, or 4.

Assume Statement 2 alone.  has congruent legs, each of measure ; since its area is 8,  can be found as follows:

From either statement alone, the length of each side of the cube, and, subsequently, the volume of the pyramid, can be calculated.

Example Question #171 : Geometry

Tetra_1

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.

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:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Explanation:

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:  

Possible Answers:

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. 

Correct answer:

Statement 1 ALONE is sufficient to answer the question, but Statement 2 ALONE is NOT sufficient to answer the question.

Explanation:

The volume of a pyramid is one third the product of its height and the area its base. 

Pyramid 1 is shown below:

Pyramid

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

Pyramid_2

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 .

Possible Answers:

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.

Correct answer:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is sufficient to answer the question.

Explanation:

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:

.

Tired of practice problems?

Try live online GMAT prep today.

1-on-1 Tutoring
Live Online Class
1-on-1 + Class
Learning Tools by Varsity Tutors