GMAT Math : Rectangular Solids & Cylinders

Study concepts, example questions & explanations for GMAT Math

varsity tutors app store varsity tutors android store

Example Questions

Example Question #5 : Dsq: Calculating The Diagonal Of A Cube

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:

Statement 2 alone is sufficient, but statement 1 alone is not sufficient 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.

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.

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 #1 : Dsq: Calculating The Surface Area Of A Cube

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:

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.

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

Both statements are needed to answer the question.

Statement II is sufficient to answer the question, but Statement I is not 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 #1 : Dsq: Calculating The Volume Of A Cube

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:

Each statement alone is 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.

Statements 1 and 2 together are not 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 #1 : 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.

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.

EITHER 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:

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 #12 : Cubes

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.

Each statement alone is enough to solve the question.

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

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

Example Question #4 : Dsq: Calculating The Volume Of A Cube

Calculate the volume of a cube. 

  1. The length of the cube's edge is .
  2. The surface area of the cube is .
Possible Answers:

Each statement alone is 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.

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.

Correct answer:

Each statement alone is sufficient to answer the question.

Explanation:

Statement 1: We need the length of the edge of the cube to calculate the volume. In this statement we're provided with the length so we just need to plug it into the equation for a cube's volume.

 

Statement 2: In this case, we need to solve for the length of the cube's edge which we can easily do: 

Now that we have our length, we can calculate the volume.

Example Question #5 : Dsq: Calculating The Volume Of A Cube

A lab has designed a cube to help with their testing procedures. Find the volume of the cube.

I) The cube will have a side length of  meters.

II) The cube will have a diagonal of meters.

Possible Answers:

Both statements are needed to answer the question.

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

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.

Either statement is sufficient to answer the question.

Correct answer:

Either statement is sufficient to answer the question.

Explanation:

Recall that the volume of a cube is equal to the cube of its side length, and that the diagonal of a cube is equal to  length. 

I) Use the following:

II) Gives us the diagonal. Divide by the square root of three, then cube it!

Either statement is sufficient to answer the question.

Example Question #1 : Dsq: Calculating The Surface Area Of A Prism

What is the volume of a cardboard box with six rectangular surfaces?

Statement 1: The length and width are each half the height.

Statement 2: The height is ten inches longer than the width.

Possible Answers:

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.

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:

To know the volume of the box, which is shaped like a rectangular prism, you multiply the length, the width, and the height together. Neither statement alone gives you those dimensions, just clues as to how they are related. But together, you can form a system of linear equations using height  and width (and length) .

By the first and second statements, respectively, 

This system can be solved:

From this, you can determine the length and height, and, subsequently, the volume.

Example Question #2 : Dsq: Calculating The Surface Area Of A Prism

A box with equal length, width, and height has the following dimensions.

I) The diagonal of the cube is .

II) The volume of the cube is .

What is the surface area of the box?

Possible Answers:

Both statements are needed to answer the question.

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.

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

Statement II is sufficient to answer the question, but statement I is not sufficient to answer the question.

Correct answer:

Either statement is sufficient to answer the question.

Explanation:

To find surface area, we need to know the side length of the box.

We are told the box has equal length, width and height. This means it is a cube.

I) Gives us the diagonal of the cube, from this we can find the side length.

, where s is the side length.

Now we can use the side length to find the surface area of the box.

 

II) Gives us the volume of the cube, from which we can also find the side length.

From here we can find the surface area.

Thus, either statement is sufficient.

Example Question #3 : Dsq: Calculating The Surface Area Of A Prism

Fry recently met a robot known for bending things. The robot wants to make a box out of steel by bending a single sheet of metal. Find the total area of the sheet of metal given the following:

I) The box will be  long.

II) The box's height will be 2 feet taller than its length, and the box's width will be  less than its length.

Possible Answers:

Either statement is 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.

Statement I is sufficient to answer the question, but statement II is not sufficient to answer the question.

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

Correct answer:

Both statements are needed to answer the question.

Explanation:

Fry recently met a robot known for bending things. The robot wants to make a box out of steel by bending a single sheet of metal. Find the total area of the sheet of metal given the following:

I) The box will be  long

II) The box's height will be 2 feet taller than its length, and the box's width will be  less than its length.

This question is a surface area question in disguise. To find the surface area of a prism, we need the area of each side. Begin by using I and II to find each side length:

Length: 36 inches or 3 feet

Height:  or 5 feet

Width:  or 

So, we have all our side lengths. Next, use the following formula for surface area of a rectangular prism:

Where l,w, and h are length, width and height

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