GMAT Math : Data-Sufficiency Questions

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #2 : Dsq: Calculating The Length Of The Side Of A Rectangle

Find the length of the side of a rectangle with a width three times the length.

  1. The area of the rectangle is .
  2. The perimeter of the rectangle 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: 

Statement 1 is sufficient to answer the question

Statement 2: 

Statement 2 is also sufficient to answer the question

Example Question #221 : Data Sufficiency Questions

A rectangle has a width measuring twice the length. Find the length.

  1. The rectangle has a perimeter of .
  2. The rectangle's area is .
Possible Answers:

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.

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

Recall the formula to find the perimeter of a rectangle. Substitute in the given information and solve.

Statement 2: 

Recall the formula for the area of a rectangle. Substitute in the given information and solve.

 

Each statement alone is sufficient to answer the question.

Example Question #3 : Rectangles

Given parallelogram  with diagonal  . Is this parallelogram a rectangle?

1) 

2) 

Possible Answers:

BOTH statements TOGETHER are sufficient to answer the question, but NEITHER statement ALONE is 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.

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 length of one diagonal alone does not prove the parallelogram to be a rectangle, nor do the lengths of the sides.

Suppose we know all of these lengths, though. Since  is a parallelogram, if , then 

The sides  and diagonal   form a triangle  with sidelengths 25, 60, and 65. The parallelogram is a rectangle if and only if  is a right angle; therefore, we must determine whether the conditions of the Pythagorean Theorem hold:

This is true;  is a right angle and  is a rectangle.

Therefore, both statements together are sufficient to answer the question, but neither statement alone is sufficient to answer the question.

Example Question #3 : Rectangles

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What is the length of the diagonal of rectangle

(1) 

(2)  and 

Possible Answers:

Each statement alone is sufficient

Statements 1 and 2 together are not sufficient

Statement 1 alone is sufficient

Both statements together are sufficient

Statement 2 alone is sufficient

Correct answer:

Statement 2 alone is sufficient

Explanation:

In order to find the diagonal, we must know the sides of the rectangle or know whether the triangles ADC or ABD have special angles.

Statement 1 alone doesn't let us calculate the hypothenuse of the triangles, because we only know one side.

Statement 2 alone is sufficient because it allows us to find all angles of the triangles inside of the rectangle. We can see that they are special triangles with angles 30-60-90. Any triangle with these angles will have its sides in ratio , where  is a constant. Here, , knowing this, we can calculate the length of the hypothenuse, also the diagonal, which will be .

 

Hence, statement 2 is sufficient.

Example Question #4 : Rectangles

Rectangle  has a perimeter of , what is its area?

I) The diagonal of  is  inches.

II) The length of one side is  inches.

Possible Answers:

Either statement alone 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 together are needed to answer the question.

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

Correct answer:

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

Explanation:

I) Gives us the length of ASOF's diagonal. This by itself does not give us any way of finding the other sides.

II) Gives us one side length. From there we can use the perimeter to find the other side length and then the area.

Therefore, Statement II is sufficient to answer the question.

Example Question #2 : Rectangles

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Rectangle , has diagonal . What is the length of ?

(1) Angle .

(2) .

Possible Answers:

Statement 2 alone is sufficient.

Statements 1 and 2 together are not sufficient.

Both statements together are sufficient.

Each statement alone is sufficient.

Statement 1 alone is sufficient.

Correct answer:

Both statements together are sufficient.

Explanation:

The length of a diagonal of a rectangle can be calculated like a hypotenuse using the Pythagorean Theorem provided we have information about the lengths of the rectangle. 

Statement 1 tells us that both triangles ADC and ABD have their angles in ratio , which means that their sides will have length in ratio , where  is a constant. We can't tell however what length the diagonal will be. 

Statment 2 tells us that side AC is 1. From there we can't conclude anything. Indeed, rectangle ABCD might as well be a square or a very thin rectangle, we don't know.

Both statements together however, allow us to tell that  and therefore that the diagonal will be 2.

Hence, both statements together are sufficient.

Example Question #2337 : Gmat Quantitative Reasoning

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 is a rectangle. What is the ratio  ?

(1) .

(2) .

Possible Answers:

Both statements together are sufficient.

Each statement alone is sufficient.

Statement 1 alone is sufficient.

Statement 1 and 2 together are not sufficient.

Statement 2 alone is sufficient.

Correct answer:

Statement 2 alone is sufficient.

Explanation:

To solve this, we need information about the lengths of the sides or to whether triangles ADB and ACD are special triangles.

Statement 1 tells us that CDA has length 3. This is not enough and we still don't know whether the rectangle is of a special type of rectangle.

Statement 2 tells us that triangles ADB and ACD are special triangles, indeed, they have their angles in ratio . That means that their sides will be in ratio . Now we don't need to know what is constant  , since it will cancel out in the ratio.

Therefore, statement 2 alone is sufficient.

Example Question #3 : Dsq: Calculating The Length Of The Diagonal Of A Rectangle

Find the diagonal of rectangle .

I) The area of  is .

II) The perimeter of  is .

Possible Answers:

Either statement is 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.

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

Correct answer:

Both statements are needed to answer the question.

Explanation:

In order to find the diagonal of a rectangle we need the length of both sides.

We can't find the lengths with just the area or just the perimeter, but by using them both together we can make a small system of equations with two unknowns and two equations.

Then we can solve for each side and use the Pythagorean Theorem to find our diagonal.

Example Question #71 : Quadrilaterals

Data sufficiency question- do not actually solve the question

Does the square or rectangle have a greater area?

1. The perimeter of both the square and rectangle are equal.

2. The rectangle does not have four equal sides.

Possible Answers:

Each statement is sufficient

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

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

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

Statements 1 and 2 are not sufficient to answer the question and more information is needed

Correct answer:

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

Explanation:

When a square and rectangle have the same perimeter, the square will have a larger area because having 4 equal sides maximizes the area. However, from statement 1, it is impossible to tell if the rectangle is also a square. When the information from statement 2 is combined, we can conclude that the rectangle is not also a square.

Example Question #1 : Dsq: Calculating The Area Of A Rectangle

What is the area of a rectangle?

Statement 1: The length of its diagonal is 25.

Statement 2: The diagonal and either of its longer sides form a  angle.

Possible Answers:

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.

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 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 find the rectangle, you need the length and the width.

If you know the diagonal  and the angle  it forms with one of the longer sides, you can use trigonometry to find both length and width:

From there, the area follows.

If you know only the diagonal, you have insufficient information; the length and width can vary according to that angle. If you only know the angle, you can discern the proportions of the sides, but not the actual lengths.

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