ISEE Upper Level Math : How to find an angle in other polygons

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

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Example Questions

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Example Question #11 : How To Find An Angle In Other Polygons

The measures of the angles of a ten-sided polygon, or decagon, form an arithmetic sequence. The least of the ten degree measures is . What is the greatest of the ten degree measures?

Possible Answers:

This polygon cannot exist.

Correct answer:

This polygon cannot exist.

Explanation:

The total of the degree measures of any ten-sided polygon is

.

In an arithmetic sequence, the terms are separated by a common difference, which we will call . Since the least of the degree measures is , the measures of the angles are

Their sum is 

The greatest of the angle measures is 

However, an angle measure cannot exceed . The correct choice is that this polygon cannot exist.

Example Question #21 : Isee Upper Level (Grades 9 12) Mathematics Achievement

Heptagon

The seven-sided polygon - or heptagon - in the above diagram is regular. What is the measure of ?

Possible Answers:

Correct answer:

Explanation:

In the diagram below, some other angles have been numbered for the sake of convenience.

Heptagon

An interior angle of a regular heptagon has measure 

.

This is the measure of .

As a result of the Isosceles Triangle Theorem, , so

.

This is also the measure of .

By angle addition, 

Again, as a result of the Isosceles Triangle Theorem, , so

Example Question #21 : Geometry

What is the sum of all the interior angles of a decagon (a polygon with ten sides)?

Possible Answers:

Correct answer:

Explanation:

The sum of the angles in a polygon can be found using the equation below, in which t is equal to the total sum of the angles, and n is equal to the number of sides. 

Example Question #14 : How To Find An Angle In Other Polygons

If each angle in a pentagon is equal to , what is the value of ?

Possible Answers:

Correct answer:

Explanation:

The sum of the angles in a polygon can be found using the equation below, in which t is equal to the total sum of the angles, and n is equal to the number of sides. 

Given that a hexagon has 6 angles, the total number of angles will be:

To find the value of each angle, we divide 540 by 5. This results in 108 degrees. 

Thus, 

Example Question #15 : How To Find An Angle In Other Polygons

What is the value of an angle (to the nearest degree) in a polygon with  sides if all the angles are equal to one another?

Possible Answers:

Correct answer:

Explanation:

The sum of the angles in a polygon can be found using the equation below, in which t is equal to the total sum of the angles, and n is equal to the number of sides. 

Given that a hexagon has 6 angles, the total number of angles will be:

Given that there are 3,600 degrees total in a polygon with 22 sides, the number of degrees in each angle can be found by dividing 3,600 by 22. To the nearest degree, this results in 164 degrees. Therefore, 164 is the correct answer.   

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