GMAT Math : DSQ: Calculating the surface area of a cube

Study concepts, example questions & explanations for GMAT Math

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Example Questions

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.

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.

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:

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:

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