ISEE Upper Level Math : Geometry

Study concepts, example questions & explanations for ISEE Upper Level Math

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Example Questions

Example Question #41 : Triangles

Triangle 2

Refer to the above figure. Express  in terms of .

Possible Answers:

Correct answer:

Explanation:

The measure of an interior angle of a triangle is equal to 180 degrees minus that of its adjacent exterior angle, so

and

.

The sum of the degree measures of the three interior angles is 180, so

Example Question #91 : Plane Geometry

Triangle 3

In the above figure, .

Give the measure of .

Possible Answers:

Correct answer:

Explanation:

 and  form a linear pair, so their degree measures total ; consequently,

 

, so by the Isosceles Triangle Theorem, 

 

The sum of the degree measures of a triangle is , so 

Example Question #10 : How To Find An Angle In An Acute / Obtuse Triangle

Triangle

Figure NOT drawn to scale.

Refer to the above figure. Evaluate .

Possible Answers:

Correct answer:

Explanation:

The measure of an exterior angle of a triangle, which here is , is equal to the sum of the measures of its remote interior angles, which here are  and . Consequently,

 and  form a linear pair and, therefore,

.

Example Question #91 : Plane Geometry

Exterior_angle

Note: Figure NOT drawn to scale.

What is the measure of angle 

Possible Answers:

Correct answer:

Explanation:

The two angles at bottom are marked as congruent. One forms a linear pair with a  angle, so it is supplementary to that angle, making its measure .  Therefore, each marked angle measures .

The sum of the measures of the interior angles of a triangle is , so:

Example Question #91 : Geometry

Which of the following is true about a triangle with two angles that measure  and ?

Possible Answers:

This triangle is scalene and right.

This triangle is scalene and obtuse.

This triangle cannot exist.

This triangle is isosceles and obtuse.

This triangle is isosceles and right.

Correct answer:

This triangle cannot exist.

Explanation:

A triangle must have at least two acute angles; however, a triangle with angles that measure  and  could have at most one acute angle, an impossible situation. Therefore, this triangle is nonexistent.

Example Question #92 : Geometry

Two sides of a scalene triangle measure 4 centimeters and 7 centimeters, and their corresponding angle measures 30 degrees. Find the area of the triangle.

Possible Answers:

Correct answer:

Explanation:

 ,

where  and   are the lengths of two sides and is the angle measure.

Plug in our given values:

Example Question #93 : Isee Upper Level (Grades 9 12) Mathematics Achievement

A scalene triangle has a base length and a corresponding altitude of . Give the area of the triangle in terms of .

Possible Answers:

Correct answer:

Explanation:

 ,

where is the base and is the altitude.

Example Question #92 : Isee Upper Level (Grades 9 12) Mathematics Achievement

What is the area of a triangle on the coordinate plane with its vertices on the points  ?

Possible Answers:

Correct answer:

Explanation:

The base can be seen as the (vertical) line segment connecting  and , which has length . The height is the pependicular distance from  to the segment; since the segment is part of the -axis, this altitude is horizontal and has length equal to -coordinate .

The area of this triangle is therefore

.

Example Question #94 : Isee Upper Level (Grades 9 12) Mathematics Achievement

What is the area of a triangle on the coordinate plane with its vertices on the points  ?

Possible Answers:

Correct answer:

Explanation:

The base can be seen as the (horizontal) line segment connecting  and , the length of which is . The height is the pependicular distance from  to the segment; since the segment is part of the -axis, this altitude is vertical and has a length equal to -coordinate

The area of this triangle is therefore

.

Example Question #53 : Triangles

Right triangle

Figure NOT drawn to scale.

 is a right triangle with altitude . What percent of  has been shaded gray?

Choose the closest answer.

Possible Answers:

Correct answer:

Explanation:

The altitude of a right triangle from the vertex of its right angle - which, here, is  - divides the triangle into two triangles similar to each other as well as the large triangle.

The similarity ratio of  to  is the ratio of the lengths of their hypotenuses. The hypotenuse of the latter is 18; that of the former, from the Pythagorean Theorem, is

The similarity ratio is therefore . The ratio of their areas is the square of this, or 

The area of  is

 

of that of , so the choice closest to the correct percent is 25%.

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