GMAT Math : GMAT Quantitative Reasoning

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #337 : Data Sufficiency Questions

Find the length of an edge of the cube.

  1. The volume of the cube is .
  2. The surface area of the cube is .
Possible Answers:

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.

Statements 1 and 2 are not sufficient, and additional data is needed 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.

Correct answer:

Each statement alone is sufficient to answer the question.

Explanation:

Statement 1:  Use the volume formula for a cube to solve for the side length.

        where  represents the length of the edge

     

 

Statement 2:   Use the surface area formula for a cube to solve for the side length.

   

   

   

Each statement alone is sufficient to answer the question.

Example Question #1 : Dsq: Calculating The Diagonal Of A Cube

 is a cube. What is the length of diagonal ?

(1) The area of a face of the cube is .

(2) The length of  is .

Possible Answers:

Each statement alone is sufficient.

Statement 2 alone is sufficient.

Statements 1 and 2 taken together are not sufficient.

Statement 1 alone is sufficient.

Both statements taken together are sufficient.

Correct answer:

Each statement alone is sufficient.

Explanation:

To know the diagonal HB of the cube, we need to have information about the length of the edges of the cube. Knowing the area of a face would allow us to find the length of an edge; therefore statement 1 alone is sufficient.

Statment 2 alone is sufficient as well since the length of a diagonal of a square is given by , where  is the length of a side of the square and ultimately we can find the length of an edge of the square.

Therefore each statement alone is sufficient.

Example Question #2 : Dsq: Calculating The Diagonal Of A Cube

Calculate the diagonal of a cube.

  1. The surface area of the cube is .
  2. The volume of the cube is .
Possible Answers:

Both statements taken together are sufficient to answer the question, but neither statement alone is sufficient.

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.

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.

Correct answer:

Each statement alone is sufficient to answer the question.

Explanation:

Statement 1: We can use the surface area to find the length of the cube's edge and then determine the length of the diagonal.

              

where  represents the length of the cube's edge

Now that we know the length of the edge, we can find the length of the diagonal: .

Statement 2: Once again, we can use the provided information to find the length of the cube's edge.

             

             

Which means the length of the diagonal is .

Thus, each statement alone is sufficient to answer the question.

Example Question #341 : Data Sufficiency Questions

Give the length of the diagonal of the cube.

  1. The surface area of the cube is .
  2. The volume of the cube is .
Possible Answers:

Statement 1 alone is sufficient, but statement 2 alone is not sufficient to answer the question.

Statements 1 and 2 are not sufficient, and additional data is needed to answer the question.

Both statements taken together are sufficient to answer the question, but neither statement alone is sufficient.

Statement 2 alone is sufficient, but statement 1 alone is not sufficient to answer the question.

Each statement alone is sufficient to answer the question.

Correct answer:

Each statement alone is sufficient to answer the question.

Explanation:

Statement 1: To find the length of the diagonal of the cube we need to find the length of the cube's edge. We can use the given surface area value to do so:

Now that we know the length of the cube's edge, we can calculate the diagonal:

 

Statement 2: We're given the volume of the cube which we can also use to solve for the length of the cube's edge.

Knowing the length of the cube's edge allows us to calculate the diagonal:

Each statement alone is sufficient to answer the question.

Example Question #342 : Data Sufficiency Questions

Find the diagonal of the cube.

  1. The surface area of the cube is .
  2. The length of an edge of the cube measures .
Possible Answers:

Each statement alone is sufficient to answer the question.

Both statements taken together are sufficient to answer the question, but neither statement alone is sufficient.

Statement 2 alone is sufficient, but statement 1 alone is not sufficient to answer the question.

Statements 1 and 2 are not sufficient, and additional data is needed to answer the question.

Statement 1 alone is sufficient, but statement 2 alone is not sufficient to answer the question.

Correct answer:

Each statement alone is sufficient to answer the question.

Explanation:

Statement 1: We need the length of an edge in order to find the diagonal of the cube. Luckily, we can find the length using the information provided:

Now that we know the length of an edge is 11 cm we can find the length of the diagonal.

 

Statement 2: We're given the information we need to find the diagonal, all we need to do is plug it into the equation

Example Question #61 : Rectangular Solids & Cylinders

What is the length of the diagonal of the cube A if the diagonal of cube B is ?

  1. The lengths of the edges of cube A to cube B is a ratio of 1:2.
  2. The surface area of cube A is .
Possible Answers:

Each statement alone is sufficient to answer the question.

Both statements taken together are sufficient to answer the question, but neither statement alone is sufficient.

Statement 2 alone is sufficient, but statement 1 alone is not sufficient to answer the question.

Statements 1 and 2 are not sufficient, and additional data is needed to answer the question.

Statement 1 alone is sufficient, but statement 2 alone is not sufficient to answer the question.

Correct answer:

Each statement alone is sufficient to answer the question.

Explanation:

Statement 1: The information provided in the question is only useful if we're given a relationship between cube A and cube B. Since this statement does provide us with the ratio of 1:2, we can answer the question.

where  represents the length of the cube's edge

we can easily see the length measures 

Remember the ratio of cube A to cube B is 1:2.

Now that we know the length, we can find the diagonal of the cube:

 

Statement 2: We're given information about cube A so we don't need to worry about cube B. Using this information we can solve for the edge length of cube A and then calculate the diagonal.

Knowing the length of the edge allows us to find the diagonal of the cube

 

Example Question #341 : Data Sufficiency Questions

Ron is making a box in the shape of a cube. He needs to know how much wood he needs. Find the surface area of the box.

I) The diagonal distance across the box will be equivalent to .

II) Half the length of one side is .

Possible Answers:

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.

Neither statement is sufficient to answer the question. More information is needed.

Either statement is sufficient to answer the question.

Correct answer:

Either statement is sufficient to answer the question.

Explanation:

To find the surface area of a cube, we need the length of one side. 

Statement I gives the diagonal, we can use this to find the length of one side.

Statement II gives us a clue about the length of one side; we can use that to find the full length of one side.

The following formula gives us the surface area of a cube:

Use Statement I to find the length of the side with the following formula, where  is the diagonal and  is the side length:

So, using Statement I, we find the surface area to be

 

Using Statement, we get that the length of one side is two times two:

Again, use the surface area formula to get the following:

Example Question #11 : Cubes

Find the volume of the cube. 

1. The cube has a diagonal of 17.32 inches.

2. The cube has a surface area of 600 square inches. 

Possible Answers:

Statements 1 and 2 together are not sufficient.

Both statements taken together are sufficient to answer the question, but neither statement alone is sufficient.

statement 1 alone is sufficient, but statement 2 alone is not sufficient to answer the question.

Each statement alone is sufficient.

Statement 2 alone is sufficient, but statement 1 alone is not sufficient to answer the question.

Correct answer:

Each statement alone is sufficient.

Explanation:

To find the volume of a cube, we only need the length of one side. Using statement 1, we can figure out the length of a side based on the diagonal. We can use the figure below to find the ratio of the diagonal to one side. If the we let the length of one side be x, we can use Pythagorean's theorem to find the length of the diagonal. So, in triangle BCD, we have a right triangle, with two sides of length x. We can set up the equation that the length of BD is .

Then we can see triangle ADB is also a right triangle. Using Pythagorean's theorem we get the length of AB is .

 Cube

So, if we divide the number from statement 1 by the square root of 3, we get the length of each side of the cube. Doing this, we get . Thus, we can solve this problem with just the information from statement 1. 

Now, we can also check statement 2. If we know the surface area of the cube, we can use that information to find the length of each side of the cube. We know that the surface area of a cube is the sum of the six faces of the cube, which all have equal area and are all squares. We can divide the total surface area by 6 to find the surface area of each square face. So, 600/6 = 100. We know that the area of a square is just the length of one side squared, so we can take the square root of 100 to find that the length of each side is 10. Thus statement 2 is also sufficient to solve this problem.

Therefore, the answer is that either statement alone is sufficient to answer the question.  

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

How much does a cube weigh?

Statement 1: The cube is made of material that weighs 3 pounds per cubic foot.

Statement 2: Each face of the cube is a square with area 16 square feet.

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 weight of a cube is dependent on its density in pounds per cubic foot and its volume in cubic feet. We need Statement 1 for the density. Statement 2 is needed for the volume - and it gives us the means to find it, since we can take the square root of the area of one side, 16, to get sidelength 4 feet, and we can cube that to get the volume of 64 cubic feet. Now we can multiply 64 cubic feet by 3 pounds per cubic foot to get 192 pounds.

Example Question #3 : Dsq: Calculating The Volume Of A Cube

Find the volume of cube W.

I) The base of W has an area of  leagues squared.

II) The diagonal of the base of W has a length of  leagues.

 

Possible Answers:

Statement 2 is sufficient to solve the question, but statement 1 is not sufficient to solve the question. 

Both statements taken together are sufficient to solve the question.

Statement 1 is sufficient to solve the question, but statement 2 is not sufficient to solve the question. 

Neither statement is sufficient to solve the question. More information is needed.

Each statement alone is enough to solve the question.

Correct answer:

Each statement alone is enough to solve the question.

Explanation:

If we know the base of W, we can find the side length. We then cube the side length to find the volume of a square. 

If we know the diagonal of the base of W, we can find the side length. As outlined above, we can then cube the side length to find the volume.

Therefore either statement alone is sufficient to solve the question.

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