ISEE Upper Level Math : Plane Geometry

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

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Example Questions

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

A trapezoid has the base lengths of and . The area of the trapezoid is . Give the height of the trapezoid in terms of .

Possible Answers:

Correct answer:

Explanation:

The area of a trapezoid is given by

,

where  are the lengths of each base and is the altitude (height) of the trapezoid.

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

In the following trapezoid  and . The area of the trapezoid is 54 square inches. Give the height of the trapezoid. Figure not drawn to scale.

Trap

Possible Answers:

Correct answer:

Explanation:

The area of a trapezoid is given by

,

where  are the lengths of each base and is the altitude (height) of the trapezoid. 

Substitute these values into the area formula:

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:

Correct answer:

Explanation:

Quadrilateral  - the shaded region - is a trapezoid with bases  and , and altitude . The area of the trapezoid can be calculated using the formula 

,

where  and  , and .

The length of  can be found by setting  and  and applying the Pythagorean Theorem:

Therefore, 

.

Substituting:

 

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

Trapezoid

Note: Figure NOT drawn to scale.

The area of the above trapezoid is . What is ?

 

Possible Answers:

Correct answer:

Explanation:

Substitute  into the formula for the area of a trapezoid:

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 inches and 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:

Correct answer:

Explanation:

To find the area of a kite, use the formula , where represents one diagnal and represents the other.

Since Cassie has one tube measuring inches, we can substitute for . We can also substitute the other tube that measures  inches in for .

Example Question #271 : Plane Geometry

Two diagonals of a kite have the lengths of and . Give the area of the kite.

Possible Answers:

Correct answer:

Explanation:

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

 ,

where and are the lengths of the diagonals. 

Example Question #272 : Geometry

In the following kite, and . Give the area of the kite. Figure not drawn to scale.

Kite

Possible Answers:

Correct answer:

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:

,

where are the lengths of two unequal sides, is the angle between them and is the sine function.

 

Example Question #2 : Kites

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:

Correct answer:

Explanation:

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

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

 

 

Example Question #1 : Kites

A kite has the area of . One of the diagonals of the kite has length . Give the length of the other diagonal of the kite.

Possible Answers:

Correct answer:

Explanation:

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

,

where and are the lengths of the diagonals. 

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

Parallelogram2

Give the area of the above parallelogram if .

Possible Answers:

Correct answer:

Explanation:

Multiply height  by base  to get the area.

By the 30-60-90 Theorem:

and

The area is therefore

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