ISEE Upper Level Quantitative : Pentagons

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

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Example Questions

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Example Question #11 : Pentagons

In Pentagon ,

The other four angles are congruent to one another.

What is ?

Possible Answers:

It is impossible for this pentagon to exist.

Correct answer:

Explanation:

The degree measures of a pentagon, which has five angles, total .

.

Let . Then since the other three angles all have the same measure as 

Therefore, we can set up, and solve for  in, the equation

Example Question #11 : Pentagons

You are given pentagon 

Which is the greater quantity?

(A) 

(B) 

Possible Answers:

(A) and (B) are equal

(A) is greater

(B) is greater

It is impossible to determine which is greater from the information given

Correct answer:

It is impossible to determine which is greater from the information given

Explanation:

It is impossible to tell, as scenarios can be constructed that would allow  to be less than, equal to, or greater than 108, keeping in mind that the sum of the degree measures of a pentagon is .

Case 1: The pentagon is regular, so all five angles are of the same measure:

This fits the conditions of the problem and makes the two quantities equal.

Case 2: 

The sum of the angle measures is therefore 

This also fits the conditions of the problem, and makes (B) greater.

Example Question #131 : Geometry

Angles

Note: Figure NOT drawn to scale

In the above figure,  and  are adjacent sides of a regular pentagon;  and  are adjacent sides of a regular hexagon. Which of the following is the greater quantity?

(a) 

(b) 

Possible Answers:

It cannot be determined which of (a) and (b) is greater

(b) is the greater quantity

(a) and (b) are equal

(a) is the greater quantity

Correct answer:

(a) is the greater quantity

Explanation:

Extend  as seen below:

Angles

, as an interior angle of a regular pentagon (five-sided polygon), has measure

.

Its exterior angle  has measure .

 

, as an interior angle of a regular hexagon (six-sided polygon), has measure

.

Its exterior angle  has measure .

Add the measures of  and  to get that of :

.

.

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