ISEE Upper Level Math : Geometry

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

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Example Questions

Example Question #271 : Isee Upper Level (Grades 9 12) Mathematics Achievement

A trapezoid has the base lengths of \displaystyle t and \displaystyle 3t. The area of the trapezoid is \displaystyle 8t^2. Give the height of the trapezoid in terms of \displaystyle t.

Possible Answers:

\displaystyle 5t

\displaystyle 8t

\displaystyle 6t

\displaystyle 4t

\displaystyle 2t

Correct answer:

\displaystyle 4t

Explanation:

The area of a trapezoid is given by

\displaystyle Area=(\frac{b_{1}+b_{2}}{2})h,

where \displaystyle b_{}1\displaystyle b_{}2 are the lengths of each base and \displaystyle h is the altitude (height) of the trapezoid.

\displaystyle Area=(\frac{b_{1}+b_{2}}{2})h=(\frac{3t+t}{2})\times h=8t^2\Rightarrow (2t)h=8t^2

\displaystyle \Rightarrow h=\frac{8t^2}{2t}=4t

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

In the following trapezoid \displaystyle b=2a and \displaystyle a=h. The area of the trapezoid is 54 square inches. Give the height of the trapezoid. Figure not drawn to scale.

Trap

Possible Answers:

\displaystyle 4\ in

\displaystyle 5\ in

\displaystyle 7\ in

\displaystyle 3\ in

\displaystyle 6\ in

Correct answer:

\displaystyle 6\ in

Explanation:

The area of a trapezoid is given by

\displaystyle Area=(\frac{b_{1}+b_{2}}{2})h,

where \displaystyle b_{}1\displaystyle b_{}2 are the lengths of each base and \displaystyle h is the altitude (height) of the trapezoid. 

\displaystyle b_{1}=a

\displaystyle b_{2}=b=2a

\displaystyle h=a

Substitute these values into the area formula:

\displaystyle Area=(\frac{b_{1}+b_{2}}{2})h=(\frac{a+2a}{2})a=54\Rightarrow \frac{3a^2}{2}=54\Rightarrow a^2=36\Rightarrow a=6\ in

Example Question #4 : How To Find The Area Of A Trapezoid

Square 3

What is the area of the shaded portion of the above square?

Possible Answers:

\displaystyle 401

\displaystyle 408

\displaystyle 492

\displaystyle 551

Correct answer:

\displaystyle 492

Explanation:

Quadrilateral \displaystyle SQUR - the shaded region - is a trapezoid with bases \displaystyle \overline{SR} and \displaystyle \overline{QU }, and altitude \displaystyle \overline{SQ}. The area of the trapezoid can be calculated using the formula 

\displaystyle A = \frac{1}{2} ( b_{1}+ b_{2} ) h,

where \displaystyle b_{1} = SR = 24 and  \displaystyle b_{2} = QU, and \displaystyle h = SQ = 25.

The length of \displaystyle \overline{UA} can be found by setting \displaystyle c = 25 and \displaystyle b = 24 and applying the Pythagorean Theorem:

\displaystyle a = \sqrt{c^{2} - b^{2}} = \sqrt{25^{2} - 24^{2}} =\sqrt{625- 576} = \sqrt{49} = 7

Therefore, 

\displaystyle QU = QA - UA = 24 - 7 = 17.

Substituting:

\displaystyle A = \frac{1}{2} ( b_{1}+ b_{2} ) h

\displaystyle A = \frac{1}{2} ( 24 + 17) 24

\displaystyle A = \frac{1}{2} \cdot 41 \cdot 24

\displaystyle A = 492

 

Example Question #272 : Isee Upper Level (Grades 9 12) Mathematics Achievement

Trapezoid

Note: Figure NOT drawn to scale.

The area of the above trapezoid is \displaystyle 465. What is \displaystyle B?

 

Possible Answers:

\displaystyle B = 42

\displaystyle B = 47

\displaystyle B = 37

\displaystyle B = 35

\displaystyle B = 31

Correct answer:

\displaystyle B = 37

Explanation:

Substitute \displaystyle A = 465, b = 25, h = 15 into the formula for the area of a trapezoid:

\displaystyle \frac{1}{2} (B + b)h = A

\displaystyle \frac{1}{2} (B + 25) \cdot 15 = 465

\displaystyle 2 \cdot \frac{1}{2} (B + 25) \cdot 15 = 2 \cdot 465

\displaystyle (B + 25) \cdot 15 = 930

\displaystyle 15 B + 375 = 930

\displaystyle 15 B + 375 - 375 = 930 - 375

\displaystyle 15 B = 555

\displaystyle 15 B \div 15 = 555\div 15

\displaystyle B = 37

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

Cassie is making a kite for her little brother.  She has two plastic tubes to use as the skeleton, measuring \displaystyle 7 inches and \displaystyle 12 inches.  If these two tubes represent the diagnals of the kite, how many square inches of paper will she need to make the kite?

Possible Answers:

\displaystyle 40

\displaystyle 84

\displaystyle 82

\displaystyle 42

\displaystyle 84

Correct answer:

\displaystyle 42

Explanation:

To find the area of a kite, use the formula \displaystyle \frac{1}{2}ab, where \displaystyle a represents one diagnal and \displaystyle b represents the other.

Since Cassie has one tube measuring \displaystyle 7 inches, we can substitute \displaystyle 7 for \displaystyle a. We can also substitute the other tube that measures \displaystyle 12 inches in for \displaystyle b.

\displaystyle \frac{1}{2}(7)(12)=42\ in^{2}

Example Question #2 : How To Find The Area Of A Kite

Two diagonals of a kite have the lengths of \displaystyle 10\ in and \displaystyle 6\ in. Give the area of the kite.

Possible Answers:

\displaystyle 45\ in^2

\displaystyle 60\ in^2

\displaystyle 36\ in^2

\displaystyle 30\ in^2

\displaystyle 80\ in^2

Correct answer:

\displaystyle 30\ in^2

Explanation:

The area of a kite is half the product of the diagonals, i.e.

 \displaystyle Area=\frac{d_{1}d_{2}}{2},

where \displaystyle d_{1} and \displaystyle d_{2} are the lengths of the diagonals. 

\displaystyle Area=\frac{d_{1}d_{2}}{2}=\frac{6\times 10}{2}=30\ in^2

Example Question #272 : Geometry

In the following kite, \displaystyle a=10\ cm\displaystyle b=15\ cm and \displaystyle \angle C=120^{\circ}. Give the area of the kite. Figure not drawn to scale.

Kite

Possible Answers:

\displaystyle 150\sqrt{3}\ cm^2

\displaystyle 150\ cm^2

\displaystyle 75\sqrt{3}\ cm^2

\displaystyle 75\sqrt{2}\ cm^2

\displaystyle 75\ cm^2

Correct answer:

\displaystyle 75\sqrt{3}\ cm^2

Explanation:

When you know the length of two unequal sides of a kite and their included angle, the following formula can be used to find the area of a kite:

\displaystyle Area=ab\times sinC,

where \displaystyle a,bare the lengths of two unequal sides, \displaystyle C is the angle between them and \displaystyle sin is the sine function.

\displaystyle Area=ab\times sinC=10\times 15\times sin120^{\circ}=10\times 15\times \frac{\sqrt{3}}{2}\Rightarrow Area=75\sqrt{3}\ cm^2

 

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

Find the area of a kite with one diagonal having length 18in and the other diagonal having a length that is half the first diagonal.

Possible Answers:

\displaystyle 54\text{in}^2

\displaystyle 162\text{in}^2

\displaystyle 81\text{in}^2

\displaystyle 76\text{in}^2

\displaystyle 108\text{in}^2

Correct answer:

\displaystyle 81\text{in}^2

Explanation:

To find the area of a kite, we will use the following formula:

\displaystyle A = \frac{pq}{2}

where and q are the lengths of the diagonals of the kite.

 

Now, we know the length of one diagonal is 18in.  We also know the other diagonal is half of the first diagonal.  Therefore, the second diagonal has a length of 9in.

Knowing this, we can substitute into the formula.  We get

\displaystyle A = \frac{18\text{in} \cdot 9\text{in}}{2}

 

\displaystyle A = \frac{162\text{in}^2}{2}

 

\displaystyle A = 81\text{in}^2

Example Question #51 : Quadrilaterals

A kite has the area of \displaystyle 60\ in^2. One of the diagonals of the kite has length \displaystyle 15\ in. Give the length of the other diagonal of the kite.

Possible Answers:

\displaystyle 7\ in

\displaystyle 8\ in

\displaystyle 4\ in

\displaystyle 6\ in

\displaystyle 5\ in

Correct answer:

\displaystyle 8\ in

Explanation:

The area of a kite is half the product of the diagonals, i.e.

\displaystyle Area=\frac{d_{1}d_{2}}{2},

where \displaystyle d_{1} and \displaystyle d_{2} are the lengths of the diagonals. 

\displaystyle Area=\frac{d_{1}d_{2}}{2}=\frac{{15}\times {d_{2}}}{2}=60\Rightarrow d_{2}=\frac{60\times 2}{15}\Rightarrow d_{2}=8\ in

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

Parallelogram2

Give the area of the above parallelogram if \displaystyle BC = 10.

Possible Answers:

\displaystyle 25\sqrt{2}

\displaystyle 25\sqrt{3}

\displaystyle 25

\displaystyle 50

\displaystyle 50\sqrt{2}

Correct answer:

\displaystyle 25\sqrt{3}

Explanation:

Multiply height \displaystyle BD by base \displaystyle CD to get the area.

By the 30-60-90 Theorem:

and

\displaystyle CD =BD \cdot \sqrt{3} = 5\sqrt{3}

The area is therefore

\displaystyle BD \cdot CD = 5 \cdot 5\sqrt{3} = 25\sqrt{3}

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