# ISEE Upper Level Quantitative : Quadrilaterals

## Example Questions

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### Example Question #1 : Other Quadrilaterals

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

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 : Other Quadrilaterals

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

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 #3 : Other Quadrilaterals

The angles of Quadrilateral A measure

The angles of Pentagon B measure

Which is the greater quantity?

(A)

(B)

(A) is greater

(A) and (B) are equal

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

(B) is greater

(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 #4 : Other Quadrilaterals

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

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 #1 : Squares

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

(a) and (b) are equal.

(b) is greater.

It is impossible to tell from the information given.

(a) is greater.

(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 #201 : 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

(b) is greater.

(a) is greater.

It is impossible to tell from the information given.

(a) and (b) are equal.

(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 #3 : 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

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

(A) and (B) are equal

(B) is greater

(A) is greater

(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 #202 : Geometry

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

(A) and (B) are equal

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

(A) is greater

(B) is greater

(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.

### Example Question #5 : Squares

The area of a square is .

Give the perimeter of the square.

Explanation:

The length of one side of a square is the square root of its area. The polynomial representing the area of the square can be recognized as a perfect square trinomial:

Therefore, the square root of the area is

,

which is the length of one side.

The perimeter of the square is four times this length, or

.

### Example Question #6 : Squares

The perimeters of six squares form an arithmetic sequence. The second-smallest square has sides that are two inches longer than those of the smallest square.

Which, if either, is the greater quantity?

(a) The perimeter of the third-smallest square

(b) The length of one side of the largest square

(a) is greater

(b) is greater

(a) and (b) are equal

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

(a) is greater

Explanation:

Let the length of one side of the first square be . Then the length of one side of the second-smallest square is , and the perimeters of the squares are

and

This makes the common difference of the perimeters 8 units.

The perimeters of the squares being in arithmetic progression, the perimeter of the th-smallest square is

Since , this becomes

The perimeter of the third-smallest square is

The perimeter of the largest, or sixth-smallest, square is

The length of one side of this square is one fourth of this, or

Therefore, we are comparing  and .

Since a perimeter must be positive,

;

also, .

Therefore, regardless of the value of ,

,

and

,

making (a) the greater quantity.

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