ISEE Upper Level Quantitative : Parallelograms

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

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Example Questions

Example Question #251 : Plane Geometry

Parallelogram

In the above parallelogram, \(\displaystyle \angle 1\) is acute. Which is the greater quantity?

(A) The area of the parallelogram

(B) 120 square inches

Possible Answers:

(A) is greater

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

(B) is greater

(A) and (B) are equal

Correct answer:

(B) is greater

Explanation:

Since \(\displaystyle \angle 1\) is acute, a right triangle can be constructed with an altitude as one leg and a side as the hypotenuse, as is shown here. The height of the triangle must be less than its sidelength of 8 inches.

Parallelogram

The height of the parallelogram must be less than its sidelength of 8 inches.

The area of the parallelogram is the product of the base and the height - which is \(\displaystyle A = 15 \cdot n\)

 Therefore, 

\(\displaystyle n < 8\)

\(\displaystyle 15 \cdot n < 15 \cdot 8\)

\(\displaystyle A < 120\)

(B) is greater.

 

Example Question #51 : Quadrilaterals

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 area of parallelogram A

(B) The area of parallelogram B

Possible Answers:

It is impossible to determine 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 area of a parallelogram is the product of its height and its base; its slant length is irrelevant. Both parallelograms have the same height (8 inches) and the same base (1 foot, or 12 inches), so they have the same areas.

Example Question #3 : How To Find The Area Of A Parallelogram

Parallelogram

Figure NOT drawn to scale

The above figure shows Rhombus \(\displaystyle ABCD\)\(\displaystyle X\) and \(\displaystyle Y\) are midpoints of their respective sides. Rectangle \(\displaystyle AXCY\) has area 150. 

Give the area of Rhombus \(\displaystyle ABCD\).

Possible Answers:

\(\displaystyle 225\)

\(\displaystyle 450\)

\(\displaystyle 300\)

\(\displaystyle 375\)

Correct answer:

\(\displaystyle 300\)

Explanation:

A rhombus, by definition, has four sides of equal length. Therefore, \(\displaystyle AB= CD\). Also, since \(\displaystyle X\) and \(\displaystyle Y\) are the midpoints of their respective sides, 

\(\displaystyle AX = XB = \frac{1}{2 }AB=\frac{1}{2 } CD = CY = YD\)

We will assign \(\displaystyle n\) to the common length of the four half-sides of the rhombus.

Also, both \(\displaystyle \overline{AY}\) and \(\displaystyle \overline{XC}\) are altitudes of the rhombus; the are congruent, and we will call their common length \(\displaystyle h\) (height).

The figure, with the lengths, is below.

Rhombus

Rectangle \(\displaystyle AXCY\) has dimensions \(\displaystyle h\) and \(\displaystyle n\); its area, 150, is the product of these dimensions, so

\(\displaystyle A_{1} = hn = 150\)

The area of the entire Rhombus \(\displaystyle ABCD\) is the product of its height \(\displaystyle h\) and the length of a base \(\displaystyle 2n\), so

\(\displaystyle A = h \cdot 2n = 2hn = 2 \cdot hn = 2 \cdot 150 = 300\).

Example Question #261 : Geometry

Parallelogram

In the above parallelogram, \(\displaystyle \angle 1\) is acute. Which is the greater quantity?

(A) The perimeter of the parallelogram

(B) 46 inches

Possible Answers:

(B) is greater

(A) is greater

(A) and (B) are equal

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

Correct answer:

(A) and (B) are equal

Explanation:

The measure of \(\displaystyle \angle 1\) 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

\(\displaystyle P = 8 + 15 + 8 + 15 = 46\) inches, 

making the quantities equal.

 

Example Question #262 : 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:

(A) is greater

(B) is greater

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

(A) and (B) are equal

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 

\(\displaystyle 12 + 12 + 12 + 12 = 48\) inches;

The perimeter of parallelogram B is 

\(\displaystyle 12 + 10 + 12 + 10 = 46\) inches.

(A) is greater.

Example Question #263 : Plane Geometry

Parallelogram

Figure NOT drawn to scale.

The above figure depicts Rhombus \(\displaystyle ABCD\) with \(\displaystyle AB = 32\) and \(\displaystyle AY = 24\).

Give the perimeter of Rhombus \(\displaystyle ABCD\).

Possible Answers:

\(\displaystyle 576\)

\(\displaystyle 112\)

\(\displaystyle 128\)

\(\displaystyle 96\)

Correct answer:

\(\displaystyle 128\)

Explanation:

All four sides of a rhombus have the same length, so we can find the perimeter of Rhombus \(\displaystyle ABCD\) by taking the length of one side and multiplying it by four. Since \(\displaystyle AB = 32\), the perimeter is four times this, or \(\displaystyle 4 \cdot AB = 4 \cdot 32 = 128\).

Note that the length of \(\displaystyle \overline{AY}\) is actually irrelevant to the problem.

Example Question #263 : Geometry

In Parallelogram \(\displaystyle ABCD\), \(\displaystyle AB = 4x\) and \(\displaystyle BC = 3y\). Which of the following is greater?

(A) \(\displaystyle x\)

(B) \(\displaystyle y\)

Possible Answers:

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

(a) and (b) are equal

(b) is the greater quantity

(a) is the greater quantity

Correct answer:

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

Explanation:

In Parallelogram \(\displaystyle ABCD\), \(\displaystyle \overline{AB}\) and \(\displaystyle \overline{BC }\) are adjoining sides; there is no specific rule for the relationship between their lengths. Therefore, no conclusion can be drawn of \(\displaystyle AB\) and \(\displaystyle BC\), and no conclusion can be drawn of the relationship between \(\displaystyle x\) and \(\displaystyle y\).

Example Question #3 : Parallelograms

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

Possible Answers:

\(\displaystyle 102^{\circ }, 94 ^{\circ }, 86^{\circ }, 78 ^{\circ }\)

\(\displaystyle 57^{\circ }, 123 ^{\circ }, 57^{\circ }, 123 ^{\circ }\)

\(\displaystyle 77^{\circ }, 133 ^{\circ }, 77^{\circ }, 133 ^{\circ }\)

\(\displaystyle 38^{\circ }, 142 ^{\circ }, 28^{\circ }, 152 ^{\circ }\)

\(\displaystyle 88^{\circ }, 97 ^{\circ }, 88^{\circ }, 97 ^{\circ }\)

Correct answer:

\(\displaystyle 57^{\circ }, 123 ^{\circ }, 57^{\circ }, 123 ^{\circ }\)

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 \(\displaystyle 38^{\circ }, 142 ^{\circ }, 28^{\circ }, 152 ^{\circ }\) and \(\displaystyle 102^{\circ }, 94 ^{\circ }, 86^{\circ }, 78 ^{\circ }\) as choices. 

Also, the sum of the measures of the angles of any quadrilateral must be \(\displaystyle 360 ^{\circ }\), so we add the angle measures of the remaining choices:

 

\(\displaystyle 88^{\circ }, 97 ^{\circ }, 88^{\circ }, 97 ^{\circ }\)

\(\displaystyle 88^{\circ } + 97 ^{\circ } + 88^{\circ }+ 97 ^{\circ } = 370\), so we can eliminate this choice.

 

\(\displaystyle 77^{\circ }, 133 ^{\circ }, 77^{\circ }, 133 ^{\circ }\):

\(\displaystyle 77^{\circ } + 133 ^{\circ } + 77^{\circ }+ 133 ^{\circ } =420\), so we can eliminate this choice.

 

\(\displaystyle 57^{\circ }, 123 ^{\circ }, 57^{\circ }, 123 ^{\circ }\)

\(\displaystyle 57^{\circ } +123 ^{\circ }+57^{\circ }+123 ^{\circ } = 360\); this is the correct choice.

Example Question #262 : Geometry

Parallelogram

 

Refer to the above figure, which shows a parallelogram. What is \(\displaystyle x + y\) equal to?

Possible Answers:

\(\displaystyle 337\)

Not enough information is given to answer this question.

\(\displaystyle 327\)

\(\displaystyle 157\)

\(\displaystyle 147\)

Correct answer:

\(\displaystyle 157\)

Explanation:

The sum of two consecutive angles of a parallelogram is \(\displaystyle 180^{\circ }\).

\(\displaystyle (x+23) + y = 180\)

\(\displaystyle x + y +23= 180\)

\(\displaystyle x + y +23 -23= 180-23\)

\(\displaystyle x + y = 157\)

157 is the correct choice.

Example Question #267 : Plane Geometry

In Parallelogram \(\displaystyle ABCD\), \(\displaystyle m \angle A = (3x)^{\circ }\) and \(\displaystyle m \angle C = (2y)^{\circ }\).

Which is the greater quantity?

(a) \(\displaystyle x\)

(b) \(\displaystyle y\)

Possible Answers:

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

(b) is the greater quantity

(a) is the greater quantity

(a) and (b) are equal

Correct answer:

(b) is the greater quantity

Explanation:

In Parallelogram \(\displaystyle ABCD\), \(\displaystyle \angle A\) and \(\displaystyle \angle C\) are opposite angles and are therefore congruent. This means that

\(\displaystyle m \angle A = m \angle C\)

\(\displaystyle 3x= 2y\)

\(\displaystyle 3x \div 3 = 2y \div 3\)

\(\displaystyle x = \frac{2}{3}y\)

Both are positive, so \(\displaystyle x< y\).

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