GMAT Math : Geometry

Study concepts, example questions & explanations for GMAT Math

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Example Questions

Example Question #1 : Understanding Intersecting Lines

Lines

Which of the following is not a valid name for the triangle in the above diagram?

Possible Answers:

All of the names in the other four choices are valid names for the triangle.

Correct answer:

All of the names in the other four choices are valid names for the triangle.

Explanation:

A triangle can be named after its three vertices in any order. Since the vertices of the triangle are , any name that includes these three letters is valid. All of the choices fit this description.

Example Question #2 : Understanding Intersecting Lines

Lines

Refer to the above diagram.

Which of the following is not a valid alternative name for  ?

Possible Answers:

Correct answer:

Explanation:

An angle can be given a name with three letters if the middle letter is the name of the vertex and the other two letters denote points on different sides of the angle. All four of the three-letter choices fit this description.

An angle can be given a one-letter name if the letter is the name of the vertex and if it is the only angle shown in the diagram to have that vertex (thereby avoiding ambiguity). There are four angles in the diagram with vertex , so we cannot use  to indicate any of them, including  is the correct choice.

Example Question #3 : Understanding Intersecting Lines

Lines

 and which angle form a linear pair?

Possible Answers:

There is no angle that forms a linear pair with .

Correct answer:

Explanation:

Two angles form a linear pair if they have the same vertex, they share one side, and their interiors do not intersect.  has vertex  and sides  and  has vertex , shares side , and shares no interior points, so this is the correct choice.

Example Question #4 : Understanding Intersecting Lines

Lines

Note: Figure NOT drawn to scale.

Refer to the above diagram. Which is a valid alternative name for  ?

Possible Answers:

Correct answer:

Explanation:

A line segment is named after its two endpoints in either order;  is the segment with endpoints  and , so it can also be named 

Example Question #5 : Understanding Intersecting Lines

Lines

 and which angle are examples of a pair of vertical angles?

Possible Answers:

There is no angle that forms a vertical pair with .

Correct answer:

Explanation:

Two angles are vertical if they have the same vertex and if their sides form two pairs of opposite rays. The correct choice will have vertex , which is the vertex of . Its rays will be the rays opposite  and , which, are, respectively,   and , respectively. The angle that fits this description is

Example Question #4 : Understanding Intersecting Lines

At what point do  and  intersect?

Possible Answers:

Correct answer:

Explanation:

To find where two lines intersect, simply set them equal to each other and solve for . Then plug the resulting  value back in to one of the equations and solve for .

Add  to both sides and subtract  from both sides to isolate our like terms:

So,  must be true for where these lines intersect. Next, plug  back in for  in one of our original equations:

So, the  value of our intersection is .

This makes the coordinate of our intersection .

You can check your answer by plugging in the point you calculated into both equations. Both equations will be true when  is equal to  and —in this case,  and —is equal to .

Example Question #433 : Geometry

What is the perimeter of a hexagon?

1) Each side measures 10 cm

2) The hexagon is regular.

Possible Answers:

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

BOTH statements TOGETHER are sufficient, but neither statement ALONE is sufficient.

Statements 1 and 2 TOGETHER are not sufficient.

EACH statement ALONE is sufficient.

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

Correct answer:

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

Explanation:

The perimeter is the sum of the measures of the sidelengths.

Knowing that the hexagon is regular only tells you the six sides are congruent; without the measure of any side, this does not help you. 

Knowing only that each of the six sides measures 10 cm is by itself enough to calculate the perimeter to be

.

The answer is that Statement 1 is sufficient, but not Statement 2.

Example Question #2 : Polygons

Figure

Note: Figure NOT drawn to scale

What is the perimeter of the above figure?

Assume all angles shown in the figure are right angles.

Possible Answers:

Not enough information is given to answer the question.

Correct answer:

Explanation:

This figure can be seen as a smaller rectangle cut out of a larger one; refer to the diagram below.

Figure

We can fill in the missing sidelengths using the fact that a rectangle has congruent opposite sides. Once this is done, we can add the lengths of the sides to get the perimeter:

 feet.

Example Question #2 : Calculating The Perimeter Of A Polygon

What is the perimeter of a rectangle with a length of  and a width of ?

Possible Answers:

Correct answer:

Explanation:

The perimeter  of any figure is the sum of the lengths of its sides. Since we have a rectangle with a length of  and a width of , we know that there will be two sides of length  and two sides of width . Therefore:

Example Question #2 : Calculating The Perimeter Of A Polygon

What is the perimeter of a right triangle with a base of  and a height of ?

Possible Answers:

Not enough information provided

Correct answer:

Explanation:

In order to find the perimeter  of the right triangle, we need to know the lengths of each of its sides. While we are given two sides - the base  and the height  - we do not know the hypotenuse . There are two ways that we can find , the first of which is the direct application of the Pythagorean Theorem: 

We could have also noted that  is a common Pythagorean Triple and deduced the value of  that way.

Now that we have all three side lengths, we can calculate :

 

 

 

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