SSAT Upper Level Math : Properties of Triangles

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

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Example Questions

Example Question #142 : Geometry

If James traveled north \(\displaystyle 30\textup { miles}\) and John traveled \(\displaystyle 40\textup { miles}\) west from the same town, how many miles away will they be from each other when they reach their destinations?

Possible Answers:

\(\displaystyle 30\textup { miles}\)

\(\displaystyle 50\textup { miles}\)

\(\displaystyle 60\textup { miles}\)

\(\displaystyle 40\textup { miles}\)

\(\displaystyle 10\textup { miles}\)

Correct answer:

\(\displaystyle 50\textup { miles}\)

Explanation:

The distances when put together create a right triangle.  

The distance between them will be the hypotenuse or the diagonal side.  

You use Pythagorean Theorem or \(\displaystyle a^{2}+b^{2}=c^{2}\) to find the length.  

So you plug \(\displaystyle 30\) and \(\displaystyle 40\) for \(\displaystyle a\) and \(\displaystyle b\) which gives you,

 \(\displaystyle 900+1600=c^{2}\) or \(\displaystyle 2500=c^{2}\).  

Then you find the square root of each side and that gives you your answer of \(\displaystyle c=50\).

Example Question #1 : How To Find The Height Of A Right Triangle

If the hypotenuse of a right triangle is 20, and one of the legs is 12, what is the value of the other leg?

Possible Answers:

\(\displaystyle 14\)

\(\displaystyle 16\)

\(\displaystyle 10\)

\(\displaystyle 12\)

Correct answer:

\(\displaystyle 16\)

Explanation:

The triangle in this problem is a variation of the 3, 4, 5 right triangle. However, it is 4 times bigger. We know this because \(\displaystyle 5\cdot4=20\) (the length of the hypotenuse) and \(\displaystyle 3\cdot4=12\) (the length of one of the legs). 

Therefore, the length of the other leg will be equal to:

\(\displaystyle 4\cdot4=16\)

Example Question #2 : How To Find The Height Of A Right Triangle

A given right triangle has a base of length \(\displaystyle 9cm\) and a total area of \(\displaystyle 45cm^{2}\). What is the height of the right triangle?

Possible Answers:

\(\displaystyle 9cm\)

\(\displaystyle 5cm\)

\(\displaystyle 10cm\)

Not enough information provided

\(\displaystyle 8cm\)

Correct answer:

\(\displaystyle 10cm\)

Explanation:

For a given right triangle with base \(\displaystyle b\) and height \(\displaystyle h\), the area \(\displaystyle A\) can be defined by the formula \(\displaystyle A=\frac{1}{2}bh\). If one leg of the right triangle is taken as the base, then the other leg is the height.  

Therefore, to find the height \(\displaystyle h\), we restructure the formula for the area \(\displaystyle A\) as follows:

\(\displaystyle A=\frac{1}{2}bh\)

\(\displaystyle 2A=bh\)

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

Plugging in our values for \(\displaystyle A\) and \(\displaystyle b\):

\(\displaystyle \frac{2(45cm^{2})}{9cm}=h\)

\(\displaystyle \frac{90cm^{2}}{9cm}=h\)

\(\displaystyle 10cm=h\)

Example Question #3 : How To Find The Height Of A Right Triangle

A given right triangle has a base length of \(\displaystyle 10cm\) and a total area of \(\displaystyle 100cm^{2}\). What is the height of the triangle?

Possible Answers:

\(\displaystyle 10cm\)

\(\displaystyle 5cm\)

Not enough information provided

\(\displaystyle 90cm\)

\(\displaystyle 20cm\)

Correct answer:

\(\displaystyle 20cm\)

Explanation:

For a given right triangle with base \(\displaystyle b\) and height \(\displaystyle h\), the area \(\displaystyle A\) can be defined by the formula \(\displaystyle A=\frac{1}{2}bh\). If one leg of the right triangle is taken as the base, then the other leg is the height.  

Therefore, to find the height \(\displaystyle h\), we restructure the formula for the area \(\displaystyle A\) as follows:

\(\displaystyle A=\frac{1}{2}bh\)

\(\displaystyle 2A=bh\)

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

Plugging in our values for \(\displaystyle A\) and \(\displaystyle b\):

\(\displaystyle \frac{2(100cm^{2})}{10cm}=h\)

\(\displaystyle \frac{200cm^{2}}{10cm}=h\)

\(\displaystyle 20cm=h\)

Example Question #2 : How To Find The Height Of A Right Triangle

A given right triangle has a hypotenuse of \(\displaystyle 30cm\) and a total area of \(\displaystyle 200cm^{2}\). What is the height of the triangle?

Possible Answers:

Not enough information provided

\(\displaystyle 20cm\)

\(\displaystyle 25cm\)

\(\displaystyle 10cm\)

\(\displaystyle 30.77cm\)

Correct answer:

Not enough information provided

Explanation:

For a given right triangle with base \(\displaystyle b\) and height \(\displaystyle h\), the area \(\displaystyle A\) can be defined by the formula \(\displaystyle A=\frac{1}{2}bh\). If one leg of the right triangle is taken as the base, then the other leg is the height. 

However, we have not been given a base or leg length for the right triangle, only the length of the hypotenuse and the area. We therefore do not have enough information to solve for the height \(\displaystyle h\)

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

The area of a right triangle is \(\displaystyle 100m^2\). If the base of the triangle is \(\displaystyle 25m\), what is the height, in meters?

Possible Answers:

\(\displaystyle 4\)

\(\displaystyle 6\)

\(\displaystyle 8\)

\(\displaystyle 10\)

Correct answer:

\(\displaystyle 8\)

Explanation:

To find the height, plug what is given in the question into the formula used to find the area of a triangle.

\(\displaystyle \text{Area}=\frac{base\times height}{2}\)

Use the information given in the question:

\(\displaystyle \text{Base}=25\)

\(\displaystyle \text{Area}=100\)

\(\displaystyle 100=\frac{25\times height}{2}\)

Now, solve for the height.

\(\displaystyle 25\times height=200\)

\(\displaystyle height=8\)

Example Question #3 : How To Find The Height Of A Right Triangle

The area of a right triangle is \(\displaystyle 45m^2\), and the base is \(\displaystyle 15m\). What is the height, in meters?

Possible Answers:

\(\displaystyle 6\)

\(\displaystyle 5\)

\(\displaystyle 3\)

\(\displaystyle 8\)

Correct answer:

\(\displaystyle 6\)

Explanation:

To find the height, plug what is given in the question into the formula used to find the area of a triangle.

\(\displaystyle \text{Area}=\frac{base\times height}{2}\)

Use the information given in the question:

\(\displaystyle \text{Base}=15\)

\(\displaystyle \text{Area}=45\)

\(\displaystyle 45=\frac{15\times height}{2}\)

Now, solve for the height.

\(\displaystyle 15\times height=90\)

\(\displaystyle height=6\)

Example Question #7 : How To Find The Height Of A Right Triangle

The area of a right triangle is \(\displaystyle 50\textup{ in}^2\). If the base of the triangle is \(\displaystyle 10\textup{ in}\), what is the length of the height, in inches?

Possible Answers:

\(\displaystyle 20\)

\(\displaystyle 15\)

\(\displaystyle 5\)

\(\displaystyle 10\)

Correct answer:

\(\displaystyle 10\)

Explanation:

To find the height, plug what is given in the question into the formula used to find the area of a triangle.

\(\displaystyle \text{Area}=\frac{base\times height}{2}\)

Use the information given in the question:

\(\displaystyle \text{Base}=10\)

\(\displaystyle \text{Area}=50\)

\(\displaystyle 50=\frac{10\times height}{2}\)

Now, solve for the height.

\(\displaystyle 10\times height=100\)

\(\displaystyle height=10\)

Example Question #4 : Geometry

Right Triangle A has hypotenuse 25 inches and one leg of length 24 inches; Right Triangle B has hypotenuse 15 inches and one leg of length 9 inches; Rectangle C has length 16 inches. The area of Rectangle C is the sum of the areas of the two right triangles. What is the width of Rectangle C?

Possible Answers:

\(\displaystyle 17 \frac{1}{4} \textrm{ in}\)

\(\displaystyle 8 \frac{5}{8} \textrm{ in}\)

\(\displaystyle 6 \frac{7}{8} \textrm{ in}\)

\(\displaystyle 14\frac{7}{8} \textrm{ in}\)

\(\displaystyle 10 \frac{1}{2} \textrm{ in}\)

Correct answer:

\(\displaystyle 8 \frac{5}{8} \textrm{ in}\)

Explanation:

The area of a right triangle is half the product of its legs. In each case, we know the length of one leg and the hypotenuse, so we need to apply the Pythagorean Theorem to find the second leg, then take half the product of the legs:

 

Right Triangle A:

The length of the second leg is

\(\displaystyle \sqrt{25^{2} -24 ^{2}} = \sqrt{625 - 576} = \sqrt{49} = 7\) inches.

The area is 

\(\displaystyle \frac{1}{2} \times 7 \times 24 = 84\) square inches.

 

Right Triangle B:

The length of the second leg is

\(\displaystyle \sqrt{15^{2} -9 ^{2}} = \sqrt{225 - 81} = \sqrt{144} = 12\) inches.

The area is 

\(\displaystyle \frac{1}{2} \times 9 \times 12 = 54\) square inches.

 

The sum of the areas is \(\displaystyle 84 + 54 = 138\) square inches.

 

The area of a rectangle is the product of its length and its height. Therefore, the height is the quotient of the area and the length, which, for Rectangle C, is \(\displaystyle 138 \div 16 = 8 \frac{5}{8}\) inches.

 

Example Question #5 : Geometry

Right Triangle A has legs of lengths 10 inches and 14 inches; Right Triangle B has legs of length 20 inches and 13 inches; Rectangle C has length 30 inches. The area of Rectangle C is the sum of the areas of the two right triangles. What is the height of Rectangle C?

Possible Answers:

\(\displaystyle 5 \textrm{ in}\)

\(\displaystyle 6 \frac{2}{3} \textrm{ in}\)

\(\displaystyle 13\frac{1}{3} \textrm{ in}\)

Insufficient information is given to determine the height.

\(\displaystyle 10 \textrm{ in}\)

Correct answer:

\(\displaystyle 6 \frac{2}{3} \textrm{ in}\)

Explanation:

The area of a right triangle is half the product of its legs. The area of Right Triangle A is equal to \(\displaystyle \frac{1}{2} \times 10 \times 14 = 70\) square inches; that of Right Triangle B is equal to \(\displaystyle \frac{1}{2} \times 20 \times 13 = 130\) square inches. The sum of the areas is \(\displaystyle 70 + 130 = 200\) square inches, which is the area of Rectangle C.

 

The area of a rectangle is the product of its length and its height. Therefore, the height is the quotient of the area and the length, which, for Rectangle C, is \(\displaystyle 200 \div 30 = 6 \frac{2}{3}\) inches.

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