ISEE Upper Level Quantitative : Plane Geometry

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

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Example Questions

Example Question #1 : How To Find The Area Of A Parallelogram

Parallelogram

Figure NOT drawn to scale

The above figure shows Rhombus  and  are midpoints of their respective sides. Rectangle  has area 150. 

Give the area of Rhombus .

Possible Answers:

Correct answer:

Explanation:

A rhombus, by definition, has four sides of equal length. Therefore, . Also, since  and  are the midpoints of their respective sides, 

We will assign  to the common length of the four half-sides of the rhombus.

Also, both  and  are altitudes of the rhombus; the are congruent, and we will call their common length  (height).

The figure, with the lengths, is below.

Rhombus

Rectangle  has dimensions  and ; its area, 150, is the product of these dimensions, so

The area of the entire Rhombus  is the product of its height  and the length of a base , so

.

Example Question #261 : Plane Geometry

Parallelogram

In the above parallelogram,  is acute. Which is the greater quantity?

(A) The perimeter of the parallelogram

(B) 46 inches

Possible Answers:

(A) is greater

(A) and (B) are equal

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

(B) is greater

Correct answer:

(A) and (B) are equal

Explanation:

The measure of  is actually irrelevant. The perimeter of the parallelogram is the sum of its four sides; since opposite sides of a parallelogram have the same length, the perimeter is

 inches, 

making the quantities equal.

 

Example Question #262 : Plane Geometry

Parallelogram A is below:

Rhombus_1

Parallelogram B is below:

 

Parallelogram

Note: These figures are NOT drawn to scale.

Refer to the parallelograms above. Which is the greater quantity?

(A) The perimeter of parallelogram A

(B) The perimeter of parallelogram B

Possible Answers:

(B) is greater

(A) and (B) are equal

(A) is greater

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

Correct answer:

(A) is greater

Explanation:

The perimeter of a parallelogram is the sum of its sidelengths; its height is irrelevant. Also, opposite sides of a parallelogram are congruent.

The perimeter of parallelogram A is 

 inches;

The perimeter of parallelogram B is 

 inches.

(A) is greater.

Example Question #3 : Parallelograms

Parallelogram

Figure NOT drawn to scale.

The above figure depicts Rhombus  with  and .

Give the perimeter of Rhombus .

Possible Answers:

Correct answer:

Explanation:

All four sides of a rhombus have the same length, so we can find the perimeter of Rhombus  by taking the length of one side and multiplying it by four. Since , the perimeter is four times this, or .

Note that the length of  is actually irrelevant to the problem.

Example Question #4 : Parallelograms

In Parallelogram , and . Which of the following is greater?

(A)

(B)

Possible Answers:

(a) and (b) are equal

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

(a) is the greater quantity

(b) is the greater quantity

Correct answer:

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

Explanation:

In Parallelogram , and  are adjoining sides; there is no specific rule for the relationship between their lengths. Therefore, no conclusion can be drawn of and , and no conclusion can be drawn of the relationship between and .

Example Question #263 : Plane Geometry

Which of the following can be the measures of the four angles of a parallelogram?

Possible Answers:

Correct answer:

Explanation:

Opposite angles of a parallelogram must have the same measure, so the correct choice must have two pairs, each of the same angle measure. We can therefore eliminate  and  as choices. 

Also, the sum of the measures of the angles of any quadrilateral must be , so we add the angle measures of the remaining choices:

 

, so we can eliminate this choice.

 

:

, so we can eliminate this choice.

 

; this is the correct choice.

Example Question #6 : Parallelograms

Parallelogram

 

Refer to the above figure, which shows a parallelogram. What is  equal to?

Possible Answers:

Not enough information is given to answer this question.

Correct answer:

Explanation:

The sum of two consecutive angles of a parallelogram is .

157 is the correct choice.

Example Question #61 : Quadrilaterals

In Parallelogram , and .

Which 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:

(b) is the greater quantity

Explanation:

In Parallelogram , and are opposite angles and are therefore congruent. This means that

Both are positive, so .

Example Question #1 : How To Find The Length Of The Side Of A Rhombus

In Rhombus , and . Which is the greater quantity?

(A)

(B)

Possible Answers:

(a) is the greater quantity

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

(a) and (b) are equal

(b) is the greater quantity

Correct answer:

(a) is the greater quantity

Explanation:

The four sides of a rhombus, by defintion, have equal length, so

Since and are positive, .

Example Question #264 : Plane Geometry

A rhombus has diagonals of length two and one-half feet and six feet. Which is the greater quantity?

(A) The perimeter of the rhombus

(B) Four yards

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:

(A) is greater

Explanation:

It will be easier to look at these measurements as inches for the time being:

 and , so these are the lengths of the diagonals in inches.

The diagonals of a rhombus are each other's perpendicular bisector, so, as can be seen in the diagram below, one side of a rhombus and one half of each diagonal form a right triangle. If we let  be the length of one side of the rhombus, then this is the hypotenuse of that right triangle; its legs are one-half the lengths of the diagonals, or 15 and 36 inches.

Rhombus_2

By the Pythagorean Theorem, 

 

Each side of the rhombus measures 39 inches, and its perimeter is 

 inches.

Four yards is equal to  inches, so (A) is greater.

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