ISEE Upper Level Quantitative : Plane Geometry

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

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Example Questions

Example Question #61 : Circles

Inscribed angle 4

Figure NOT drawn to scale

In the above diagram, .

Which is the greater quantity?

(a) 

(b) 

Possible Answers:

(a) and (b) are equal

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

(b) is the greater quantity

(a) is the greater quantity

Correct answer:

(a) and (b) are equal

Explanation:

 is a right triangle whose hypotenuse  has length  times that of leg . This is characteristic of a triangle whose acute angles both have measure  -and consequently, whose acute angles are congruent. Therefore,

These inscribed angles being congruent, the arcs they intercept,  and , are also congruent.

 

Example Question #13 : How To Find The Angle Of A Sector

Inscribed angle 4

Figure NOT drawn to scale

In the above diagram, .

Which is the greater quantity?

(a) 

(b) 

Possible Answers:

(b) is the greater quantity

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

(a) and (b) are equal

(a) is the greater quantity

Correct answer:

(a) is the greater quantity

Explanation:

 is an inscribed angle, so its degree measure is half that of the arc it intercepts, :

.

 and  are acute angles of right triangle . They are therefore complimentary - that is, their degree measures total . Consequently,

.

Example Question #201 : Plane Geometry

Three of the interior angles of a quadrilateral measure , and . What is the measure of the fourth interior angle?

Possible Answers:

This quadrilateral cannot exist.

Correct answer:

Explanation:

The measures of the angles of a quadrilateral have sum . If  is the measure of the unknown angle, then:

The measure of the fourth angle is .

Example Question #2 : Quadrilaterals

In a certain quadrilateral, three of the angles are , , and . What is the measure of the fourth angle?

Possible Answers:

Correct answer:

Explanation:

A quadrilateral has four angles totalling . So, first add up the three angles given. The sum is . Then, subtract that from 360. This gives you the missing angle, which is .

Example Question #2 : Other Quadrilaterals

The angles of Quadrilateral A measure 

The angles of Pentagon B measure 

Which is the greater quantity?

(A) 

(B) 

Possible Answers:

(A) and (B) are equal

(B) is greater

(A) is greater

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

Correct answer:

(B) is greater

Explanation:

The sum of the measures of the angles of a quadrilateral is ; the sum of the measures if a pentagon is . Therefore, 

and 

, so (B) is greater.

Example Question #3 : Quadrilaterals

Three of the interior angles of a quadrilateral measure , and . What is the measure of the fourth interior angle?

Possible Answers:

This quadrilateral cannot exist.

Correct answer:

Explanation:

The measures of the angles of a quadrilateral have sum . If  is the measure of the unknown angle, then:

The measure of the fourth angle is .

Example Question #202 : Plane Geometry

Which is the greater quantity?

(a) The perimeter of a square with sidelength 1 meter

(b) The perimeter of a regular pentagon with sidelength 75 centimeters

Possible Answers:

(a) and (b) are equal.

It is impossible to tell from the information given.

(b) is greater.

(a) is greater.

Correct answer:

(a) is greater.

Explanation:

(a) One meter is equal to 100 centimeters; a square with this sidelength has perimeter  centimeters.

(b) A regular pentagon has five congruent sides; since the sidelength is 75 centimeters, the perimeter is  centimeters.

This makes (a) greater.

Example Question #203 : Plane Geometry

Square 1 is inscribed inside a circle. The circle is inscribed inside Square 2.

Which is the greater quantity?

(a) Twice the perimeter of Square 1

(b) The perimeter of Square 2

Possible Answers:

(b) is greater.

(a) and (b) are equal.

It is impossible to tell from the information given.

(a) is greater.

Correct answer:

(a) is greater.

Explanation:

Let  be the sidelength of Square 1. Then the length of a diagonal of this square - which is  times this sidelength, or  by the  Theorem - is the same as the diameter of this circle, which, in turn, is equal to the sidelength of Square 2. 

Since the perimeter of a square is four times its sidelength, Square 1 has perimeter ; Square 2 has perimeter , which is  times the perimeter of Square 1. , making the perimeter of Square 2 less than twice than the perimeter of Square 1.

Example Question #1 : Squares

Five squares have sidelengths one foot, two feet, three feet, four feet, and five feet.

Which is the greater quantity?

(A) The mean of their perimeters

(B) The median of their perimeters

Possible Answers:

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

(A) is greater

(A) and (B) are equal

(B) is greater

Correct answer:

(A) and (B) are equal

Explanation:

The perimeters of the squares are 

 feet

 feet

 feet

 feet

 feet

The mean of the perimeters is their sum divided by five;

 feet.

The median of the perimeters is the value in the middle when they are arranged in ascending order; this can be seen to also be 12 feet.

The quantities are equal.

Example Question #3 : Squares

Four squares have sidelengths one meter, one meter, 120 centimeters, and 140 centimeters. Which is the greater quantity?

(A) The mean of their perimeters

(B) The median of their perimeters

Possible Answers:

(A) is greater

(A) and (B) are equal

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

(B) is greater

Correct answer:

(A) is greater

Explanation:

First find the perimeters of the squares:

 centimeters (one meter being 100 centimeters)

 centimeters

 centimeters

 centimeters

The mean of the perimeters is their sum divided by four:

 feet.

The median of the perimeters is the mean of the two values in the middle, assuming the values are in numerical order:

The mean, (A), is greater.

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