ISEE Upper Level Math : Plane Geometry

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

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Example Questions

Example Question #11 : Hexagons

Find the perimeter of a hexagon with a side having a length of 7cm.

Possible Answers:

Correct answer:

Explanation:

A hexagon has 6 equal sides.  To find the perimeter of a hexagon, we will use the following formula:

where a is the length of one side of the hexagon.

Now, we know one side has a length of 7cm. So, we get

Example Question #12 : Hexagons

What is the perimeter of a hexagon with a side length of 1?

Possible Answers:

Correct answer:

Explanation:

A hexagon has 6 similar sides.

The formula to find the perimeter of a hexagon is:

Substitute the side into the equation.

The perimeter of the hexagon is .

The answer is:  

Example Question #11 : Isee Upper Level (Grades 9 12) Mathematics Achievement

If the perimeter of a septagon is equal to , what is the length of one side? (All sides of the septagon are equal.)

Possible Answers:

Correct answer:

Explanation:

If the perimeter of a septagon (in which all sides are equal) is , then the length of one side will be one seventh of this expression. 

To find one seventh, the value must first be simplified and then divided by 7. 

When this is divided by 7, the result is:

This value is thus the length of one side of the septagon. 

Example Question #11 : Geometry

How many degrees are in an internal angle of a regular heptagon?

Possible Answers:

Correct answer:

Explanation:

The number of degrees in an internal angle of a regular polygon can be solved using the following equation where n equals the number of sides in the polygon:

Example Question #12 : Geometry

What is the measure of an interior angle of a regular nonagon?

Possible Answers:

Correct answer:

Explanation:

The measure of an interior angle of a regular polygon can be determined using the following equation where n equals the number of sides:

Example Question #12 : Plane Geometry

Thingy

Note: Figure NOT drawn to scale.

Refer to the above diagram. Pentagon  is regular. What is the measure of  ?

Possible Answers:

Correct answer:

Explanation:

The answer can be more clearly seen by extending  to a ray :

Thingy

Note that angles have been newly numbered.

 and  are exterior angles of a (five-sided) regular pentagon in relation to two parallel lines, so each has a measure of  is a corresponding angle to , so its measure is also .

By angle addition, 

Example Question #13 : Isee Upper Level (Grades 9 12) Mathematics Achievement

Thingy

In the above figure, the seven-side polygon, or heptagon, shown is regular. What is the measure of  ?

Possible Answers:

The correct answer is not given among the other responses.

Correct answer:

Explanation:

The answer can be more clearly obtained by extending the top of the two parallel lines as follows:

 

Note that two angles have been newly labeled.

Thingy

 is an interior angle of a regular heptagon and therefore has measure

By the Isosceles Triangle Theorem, since the two sides of the heptagon that help form the triangle are congruent, so are the two acute angles, and

 is supplementary to , so 

Example Question #2 : How To Find An Angle In Other Polygons

Thingy

In the above figure, the seven-side polygon, or heptagon, shown is regular. What is the measure of  ?

Possible Answers:

The correct answer is not given among the other responses.

Correct answer:

Explanation:

The answer can be more clearly seen by extending the lower right side of the heptagon to a ray, as shown:

Thingy

Note that angles have been newly numbered.

 and  are exterior angles of a (seven-sided) regular heptagon, so each has a measure of  is a corresponding angle to  in relation to two parallel lines, so its measure is also .

By angle addition, 

 

Example Question #14 : Isee Upper Level (Grades 9 12) Mathematics Achievement

Pentagon

Note: Figure NOT drawn to scale.

In the above figure, Pentagon  is regular. Give the measure of .

Possible Answers:

Correct answer:

Explanation:

The sum of the degree measures of the angles of Quadrilateral  is 360, so

 

Each interior angle of a regular pentagon measures 

,

which is therefore the measure of .

 

It is also given that  and , so substitute and solve:

Example Question #3 : How To Find An Angle In Other Polygons

Pentagon

Note: Figure NOT drawn to scale.

In the above figure, Pentagon  is regular. Give the measure of .

Possible Answers:

The correct answer is not given among the other responses.

Correct answer:

Explanation:

The sum of the degree measures of the angles of Quadrilateral  is 360, so

.

 

Each interior angle of a regular pentagon measures 

,

which is therefore the measure of both  and .

 

 and  form a linear pair, making them supplementary. Since ,

.

 

Substitute and solve:

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