GMAT Math : Rectangular Solids & Cylinders
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Example Questions
Example Question #1 : Dsq: Calculating The Volume Of A Prism
Given a right square pyramid and a right cone, which, if either, has greater volume?
Statement 1: The two have the same height.
Statement 2: The base of the cone and the base of the pyramid have the same area.
BOTH statements TOGETHER are insufficient 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.
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.
Given base area 
If we know the heights of the two figures are the same, we still need to know which has the greater base area in order to know which has the greater volume, so Statement 1 is insufficient. By a similar argument, Statement 2 is insufficient.
If we know both heights are equal and that both bases have equal area, then we know that the volumes are equal.
Example Question #2 : Dsq: Calculating The Volume Of A Prism
Find the volume of a rectangular prism.
Statement 1: 
Statement 2: The diagonal is 6.
Statement 1: 
The height can be easily solved for by substituting the length and width. Height is 2, and the volume can be calculated by the following formula.
Statement 2: The diagonal is 6.
Write the equation of the diagonal in terms of length, width, and height.
Although the lengths from Statement 1 will yield a diagonal of six, there are multiple combinations of length, width, and height which will also give a diagonal of six. The product of these three dimensions may or may not give a volume of six. Statement 2 has insufficient information to calculate the volume.
Therefore:
Example Question #1 : Dsq: Calculating The Volume Of A Prism
While deep-sea diving, Al found a rectangular treasure chest. Before he opens it, he wants to find the volume of the chest. What is it?
I) Al measured the chest's longest side to be twice its smallest side and one-and-a-half times the length of the medium side.
II) Al found that the chest's shortest side is 2.5ft long.
Statement I is sufficient to answer the question, but Statement II is not sufficient to answer the question.
Either statement is sufficient to answer the question.
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.
Neither statement is sufficient to answer the question. More information is needed.
Both statements are needed to answer the question.
To find the volume of a rectangular solid, use the following formula:
Statement I relates the length, width and height of the treasure chest.
Statement II gives us the length of the shortest side of the treasure chest.
Use Statement II and the relationships described in Statement I to find each side, then multiply them all together to get your answer.
If the shortest side is 2.5ft, then the longest side must be 5ft.
If the longest side is 5ft, then the medium side can be found via the following:
So the volume is as follows:
Example Question #1 : Dsq: Calculating The Diagonal Of A Prism
Find the length of the diagonal of cube 
I) 
II) 
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.
Either statement is sufficient to answer the question.
Both statements are needed to answer the question.
Either statement is sufficient to answer the question.
To find the length of the diagonal, we need the side length.
I) Gives us the volume of the cube. Take the cubed root to find the side length.
II) Gives us the surface area, divide by 6 (the number of faces in a cube) and take the square root to find the side length.
Diagonal of a cube is the side length times the square root of three. Alternatively, this can be found using the Pythagorean Theorem twice.
Either way, we can use I) or II) to find our side lenght and then our diagonal.
Example Question #2 : Dsq: Calculating The Diagonal Of A Prism
What is the diagonal of a rectangular prism?
1) Its surface area is
2) Its height = twice its width = thrice its length.
Statement 1 alone is sufficient.
Statement 2 alone is sufficient.
Neither of the statements, separate or together, is sufficient.
Together, the two statements are sufficient.
Either of the statements is sufficient.
Together, the two statements are sufficient.
The diagonal of a rectangular prism is found via the formula
The second statement reduces this to
However, the actual length is unknown. Statement 1 allows the calculation of a numerical value:
Example Question #1 : Dsq: Calculating The Length Of An Edge Of A Prism
A carpenter is building a box to hold his tools. Find the legth of the second smallest side of the box.
I) The box will have a volume of 
II) The smallest side is half the length of the longest side and the middle side is three-quarters of the length of the longest side.
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.
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.
Neither statement is sufficient to answer the question. More information is needed.
Both statements are needed to answer the question.
Volume of a prism is found by:
We are given the volume in statement I.
We are told how the sides relate in statement II.
Put together these two statements will allow us to set up an equation to find the middle side.
Example Question #2 : Dsq: Calculating The Length Of An Edge Of A Prism
A pirate wants to hide all of his treasure. He commisions a local woodworker to build him a series of wooden chests of volume of 
I) The shortest side will be 
II) The middle side will be 2 feet long.
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.
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.
Both statements are needed to answer the question.
A pirate wants to hide all of his treasure. He commisions a local woodworker to build him a series of wooden chests of volume of 
I) The shortest side will be 
II) The middle side will be 2 feet long
Use I) and II) to find the length of the smallest side
Next, use the short and medium sides, along with info in the prompt, to find the last side:
Example Question #3 : Dsq: Calculating The Length Of An Edge Of A Prism
Find the height of a box used to ship a computer, given the following:
I) The computer, along with all the cushioning, will take up a space of 
II) The width of the box will be 
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.
Neither statement is sufficient to answer the question. More information is needed.
Both statements are needed to answer the question.
Neither statement is sufficient to answer the question. More information is needed.
Find the height of a box used to ship a computer, given the following:
I) The computer, along with all the cushioning, will take up a space of
II) The width of the box will be 
Begin by recalling the volume of a rectangular prism formula:
Where l,w and h are length, width and height.
Next, use II) to set up a relationship between w and l
Then, use the voume formula:
As you can see, we still have two unknowns, and no way of finding either.
Therefore, we do not have information.
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