ISEE Middle Level Math : Plane Geometry

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

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Example Questions

Example Question #12 : How To Find The Area Of A Triangle

Rectangles

Note: Figure NOT drawn to scale.

Refer to the above diagram. Give the ratio of the area of the green region to that of the white region.

Possible Answers:

The correct answer is not given among the other choices.

Correct answer:

Explanation:

The area of the entire rectangle is the product of its length and width, or

.

The area of the right triangle is half the product of its legs, or

The area of the green region is therefore the difference of the two, or

.

The ratio of the area of the green region to that of the white region is 

That is, 11 to 4.

Example Question #3 : Area Of A Triangle

A triangle has a height of 9 inches and a base that is one third as long as the height. What is the area of the triangle, in square inches?

Possible Answers:

None of these

Correct answer:

Explanation:

The area of a triangle is found by multiplying the base times the height, divided by 2. 

Given that the height is 9 inches, and the base is one third of the height, the base will be 3 inches.

We now have both the base (3) and height (9) of the triangle. We can use the equation to solve for the area.

The fraction cannot be simplified.

Example Question #5 : How To Find The Area Of A Triangle

If the angles of a triangle are equal to , , and , what is the value of ?

Possible Answers:

Correct answer:

Explanation:

Given that there are 180 degrees in a triangle, 

Thus, 30 is the correct answer. 

Example Question #41 : Plane Geometry

The three angles of a triangle are labeled , , and . If  is , what is the value of ?

Possible Answers:

Correct answer:

Explanation:

Given that the three angles of a triangle always add up to 180 degrees, the following equation can be used:

Example Question #42 : Plane Geometry

In an equilateral triangle, which of the following is NOT true?

Possible Answers:

There is a 60 degree angle

All angles are equal

There is a 90 degree angle

All sides are equal

Correct answer:

There is a 90 degree angle

Explanation:

In an equilateral triangle, all sides and angles are equal. All the angles equal 60 degrees, so there is a 60 degree angle.

Therefore, the answer choice, “There is a 90 degree angle” is not true and is the correct answer choice. 

Example Question #13 : How To Find The Area Of A Triangle

The hypotenuse of a right triangle is  feet; it has one leg  feet long. Give its area in square inches.

Possible Answers:

Correct answer:

Explanation:

The area of a right triangle is half the product of the lengths of its legs, so we need to use the Pythagorean Theorem to find the length of the other leg. Set :

The legs have length  and  feet; multiply both dimensions by  to convert to inches:

 inches

 inches.

Now find half the product:

Example Question #14 : How To Find The Area Of A Triangle

What is the area (in square feet) of a triangle with a base of  feet and a height of  feet?

Possible Answers:

Correct answer:

Explanation:

The area of a triangle is found by multiplying the base times the height, divided by

 

Example Question #42 : Plane Geometry

What is the area of a triangle with a base of  and a height of ?

Possible Answers:

Correct answer:

Explanation:

The formula for the area of a triangle is \dpi{100} Area=\frac{1}{2}\times base\times height.

Plug the given values into the formula to solve:

\dpi{100} Area=\frac{1}{2}\times 12\times 3

\dpi{100} Area=\frac{1}{2}\times 36

\dpi{100} Area=18

Example Question #41 : Triangles

You have two traingular gardens next to each other.  They both have a base of  and a height of .  What is the total area?

Possible Answers:

Correct answer:

Explanation:

The area of a triangle is 

 

and since there are two identical traingles, them put together will just be 

.  

So your answer will just be .

Example Question #45 : Plane Geometry

Pentagon

The above figure depicts Square  with perimeter 240. , and  are the midpoints of , and , respectively.

Give the area of Polygon .

Possible Answers:

Correct answer:

Explanation:

Square  has perimeter 240, so the length of each side is one fourth of this, or 

.

Segment , as seen below, divides Polygon  into two figures:

Pentagon 1

One figure is , with base and height 60 and 30, respectively. Its area is half their product, or 

The other figure is Rect , whose length and width are 60 and 30, respectively. Its area is their product, or

Add these areas:

.

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