GRE Math : GRE Quantitative Reasoning

Study concepts, example questions & explanations for GRE Math

varsity tutors app store varsity tutors android store varsity tutors ibooks store

Example Questions

Example Question #1 : Cubes

What is the length of the diagonal of a cube that has a surface area of  ?

Possible Answers:

Correct answer:

Explanation:

To begin, the best thing to do is to find the length of a side of the cube. This is done using the formula for the surface area of a cube. Recall that a cube is made up of  squares. Therefore, its surface area is:

, where  is the length of a side.

Therefore, for our data, we have:

Solving for , we get:

This means that 

Now, the diagonal length of a cube is found by a form of the distance formula that is akin to the Pythagorean Theorem, though with an additional dimension added to it. It is:

, or , or 

Now, if the the value of  is , we get simply 

 

Example Question #1521 : Gre Quantitative Reasoning

What is the volume of a rectangular box that is twice as long as it is high, and four times as wide as it is long?

Possible Answers:

4L3

2L3

8

5L

2L2

Correct answer:

2L3

Explanation:

The box is 2 times as long as it is high, so H = L/2. It is also 4 times as wide as it is long, so W = 4L. Now we need volume = L * W * H = L * 4L * L/2 = 2L3.

Example Question #1522 : Gre Quantitative Reasoning

What is the volume of a cube with a surface area of  ?

Possible Answers:

Correct answer:

Explanation:

The surface area of a cube is merely the sum of the surface areas of the  squares that make up its faces. Therefore, the surface area equation understandably is:

, where  is the side length of any one side of the cube. For our values, we know:

Solving for , we get:

 or 

Now, the volume of a cube is defined by the simple equation:

For , this is:

Example Question #3 : Cubes

The volume of a cube is . If the side length of this cube is tripled, what is the new volume?

Possible Answers:

Correct answer:

Explanation:

Recall that the volume of a cube is defined by the equation:

, where  is the side length of the cube. 

Therefore, if we know that , we can solve:

This means that .

Now, if we triple  to , the new volume of our cube will be:

Example Question #2 : How To Find The Volume Of A Cube

What is the volume of a cube with surface area of ?

Possible Answers:

Correct answer:

Explanation:

Recall that the equation for the surface area of a cube is merely derived from the fact that the cube's faces are made up of  squares. It is therefore:

For our values, this is:

Solving for , we get:

, so 

Now, the volume of a cube is merely:

Therefore, for , this value is:

Example Question #2 : How To Find The Volume Of A Cube

A cube has a volume of 64, what would it be if you doubled its side lengths?

Possible Answers:

Correct answer:

Explanation:

To find the volume of a cube, you multiple your side length 3 times (s*s*s).  

To find the side length from the volume, you find the cube root which gives you 4 

.  

Doubling the side gives you 8 

.  

The volume of the new cube would then be 512 

.

Example Question #331 : Geometry

A rectangular box is 6 feet wide, 3 feet long, and 2 feet high.  What is the surface area of this box?

Possible Answers:

64 sq ft

72 sq ft

22 sq ft

36 sq ft

48 sq ft

Correct answer:

72 sq ft

Explanation:

The surface area formula we need to solve this is 2ab + 2bc + 2ac.  So if we let a = 6, b = 3, and c = 2, then surface area:

= 2(6)(3) + 2(3)(2) +2(6)(2)

= 72 sq ft.

Example Question #2 : How To Find The Surface Area Of A Cube

What is the surface area of a rectangular box that is 3 feet high, 6 feet long, and 4 feet wide?

Possible Answers:

108

144

72

84

96

Correct answer:

108

Explanation:

Surface area of a rectangular solid

= 2lw + 2lh + 2wh

= 2(6)(4) + 2(6)(3) + 2(4)(3)

= 108

Example Question #1 : How To Find The Surface Area Of A Cube

A large cube is made by fitting 8 smaller, identical cubes together. If the volume of each of the smaller cubes is 27, what is the surface area of the large cube?

Possible Answers:

Correct answer:

Explanation:

Since the volume of the smaller cubes with edges, , is 27, we have:

.

The large cube has edges .

So the surface area of the large cube is:

.

Example Question #1 : How To Find The Surface Area Of A Cube

Quantity A:

The surface area of a cube with a volume of .

Quantity B:

The volume of a cube with a surface area of .

Possible Answers:

The relationshp cannot be determined from the information given. 

Both quantities are equal.

Quantity A is greater.

Quantity B is greater. 

Correct answer:

Quantity B is greater. 

Explanation:

The relationship can be determined, because it is possible to find the surface area of a cube from the volume and vice versa.

Quantity A:

To find the surface area of the cube, you must find the side length. To find the side length from the volume, you must find the cube root.  

Find the cube root of the volume.

Insert into surface area equation.

Quantity B:

To find the volume of a cube, you must find the side length. To find the side length from the surface area, you must divide by 6, then find the square root of the result. Then, cube that result.

Divide by 6.

Square root.

Now, to find the volume.

Quantity B is greater.

Tired of practice problems?

Try live online GRE prep today.

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