SSAT Upper Level Math : How to find the length of the side of a right triangle

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

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Example Questions

Example Question #671 : Ssat Upper Level Quantitative (Math)

A right triangle has a hypotenuse of 39 and one leg is 36. What is the length of the other leg?

Possible Answers:

\(\displaystyle 19\)

\(\displaystyle 3\)

\(\displaystyle 33\)

\(\displaystyle 27\)

\(\displaystyle 15\)

Correct answer:

\(\displaystyle 15\)

Explanation:

You may recognize these numbers as multiples of 13 and 12 (each by a factor of 3) and remember that sides of length 5, 12 and 13 make a special right triangle. So the other leg would be 15 \(\displaystyle (5\times 3)\).

If you don't remember this, you can use Pythagorean theorem:

\(\displaystyle 39^{2}-36^{2}= 1521-1296=225\)

\(\displaystyle \sqrt{225}=15\)

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

A right triangle has a hypotenuse of \(\displaystyle 12\) and one leg has a length of \(\displaystyle 9\). What is the length of the other leg?

Possible Answers:

\(\displaystyle 11\)

\(\displaystyle 8\)

\(\displaystyle 7\sqrt{3}\)

\(\displaystyle 10\)

\(\displaystyle 3\sqrt{7}\)

Correct answer:

\(\displaystyle 3\sqrt{7}\)

Explanation:

When calculating the lengths of sides of a right triangle, we can use the Pythagorean Theorem as follows:

\(\displaystyle a^{2}+b^{2}=c^{2}\), where \(\displaystyle a\) and \(\displaystyle b\) are legs of the triangle and \(\displaystyle c\) is the hypotenuse.

Plugging in our given values:

\(\displaystyle 9^{2}+b^{2}=12^{2}\)

Subtracting \(\displaystyle 9^2\) from each side of the equation:

\(\displaystyle b^{2}=12^{2}-9^{2}\)

\(\displaystyle b^{2}=144-81\)

\(\displaystyle b^{2}=63\)

Taking the square root of each side of the equation:

\(\displaystyle b=\sqrt{63}\)

Simplifying the square root:

\(\displaystyle b=\sqrt{9\times 7}\)

\(\displaystyle b=3\sqrt{7}\)

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

A right triangle has two legs of length \(\displaystyle 6\) and \(\displaystyle 10\), respectively. What is the hypotenuse of the right triangle?

Possible Answers:

\(\displaystyle 12\)

\(\displaystyle 2\sqrt{17}\)

\(\displaystyle 2\sqrt{34}\)

\(\displaystyle 17\sqrt{2}\)

\(\displaystyle 34\sqrt{2}\)

Correct answer:

\(\displaystyle 2\sqrt{34}\)

Explanation:

When calculating the lengths of sides of a right triangle, we can use the Pythagorean Theorem as follows:

\(\displaystyle a^{2}+b^{2}=c^{2}\), where \(\displaystyle a\) and \(\displaystyle b\) are legs of the triangle and \(\displaystyle c\) is the hypotenuse.

Plugging in our given values:

\(\displaystyle 6^{2}+10^{2}=c^{2}\)

\(\displaystyle 36+100=c^{2}\)

\(\displaystyle 136=c^{2}\)

\(\displaystyle \sqrt{136}=c\)

\(\displaystyle \sqrt{17\times 8}=c\)

\(\displaystyle \sqrt{17\times 4\times 2}=c\)

\(\displaystyle 2\sqrt{34}=c\)

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

A right triangle has a leg of length \(\displaystyle 7\) and a hypotenuse of length \(\displaystyle 11\). What is the length of the other leg?

Possible Answers:

\(\displaystyle 2\sqrt{6}\)

\(\displaystyle 6\sqrt{2}\)

\(\displaystyle 9\sqrt{6}\)

\(\displaystyle 6\sqrt{9}\)

\(\displaystyle 9\)

Correct answer:

\(\displaystyle 6\sqrt{2}\)

Explanation:

When calculating the lengths of sides of a right triangle, we can use the Pythagorean Theorem as follows:

\(\displaystyle a^{2}+b^{2}=c^{2}\), where \(\displaystyle a\) and \(\displaystyle b\) are legs of the triangle and \(\displaystyle c\) is the hypotenuse.

Plugging in our given values:

\(\displaystyle 7^{2}+b^{2}=11^{2}\)

Subtracting \(\displaystyle 7^2\) from each side of the equation:

\(\displaystyle b^{2}=11^{2}-7^{2}\)

\(\displaystyle b^{2}=121-49\)

\(\displaystyle b^{2}=72\)

\(\displaystyle b=\sqrt{72}\)

\(\displaystyle b=\sqrt{36\times 2}\)

\(\displaystyle b=6\sqrt{2}\)

Example Question #11 : Properties Of Triangles

Find the length of the missing side.

1

Possible Answers:

\(\displaystyle 160\)

\(\displaystyle 4\sqrt{10}\)

\(\displaystyle \sqrt{15}\)

\(\displaystyle 80\)

Correct answer:

\(\displaystyle 4\sqrt{10}\)

Explanation:

Use the Pythagorean Theorem to find the length of the missing side.

\(\displaystyle x^2+6^2=14^2\)

\(\displaystyle x^2+36=196\)

\(\displaystyle x^2=160\)

\(\displaystyle x=\sqrt{160}=4\sqrt{10}\)

Example Question #12 : Properties Of Triangles

Find the length of the missing side.

2

Possible Answers:

\(\displaystyle 176\)

\(\displaystyle 8\sqrt2\)

\(\displaystyle 4\sqrt{13}\)

\(\displaystyle 4\sqrt{11}\)

Correct answer:

\(\displaystyle 4\sqrt{11}\)

Explanation:

Use the Pythagorean Theorem to find the length of the missing side.

\(\displaystyle x^2+7^2=15^2\)

\(\displaystyle x^2+49=225\)

\(\displaystyle x^2=176\)

\(\displaystyle x=\sqrt{176}=4\sqrt{11}\)

Example Question #11 : Right Triangles

Find the length of the missing side.

3

Possible Answers:

\(\displaystyle 4\)

\(\displaystyle 5\)

\(\displaystyle 25\)

\(\displaystyle 8\)

Correct answer:

\(\displaystyle 5\)

Explanation:

Use the Pythagorean Theorem to find the length of the missing side.

\(\displaystyle x^2+12^2=13^2\)

\(\displaystyle x^2+144=169\)

\(\displaystyle x^2=25\)

\(\displaystyle x=\sqrt{25}=5\)

Example Question #12 : Right Triangles

Find the length of the missing side.

4

Possible Answers:

\(\displaystyle 12\)

\(\displaystyle 10\)

\(\displaystyle 100\)

\(\displaystyle 14\)

Correct answer:

\(\displaystyle 10\)

Explanation:

Use the Pythagorean Theorem to find the length of the missing side.

\(\displaystyle x^2+24^2=26^2\)

\(\displaystyle x^2+576=676\)

\(\displaystyle x^2=100\)

\(\displaystyle x=\sqrt{100}=10\)

Example Question #13 : Right Triangles

Find the length of the missing side.

5

Possible Answers:

\(\displaystyle 8\)

\(\displaystyle 64\)

\(\displaystyle 9\)

\(\displaystyle 5\)

Correct answer:

\(\displaystyle 8\)

Explanation:

Use the Pythagorean Theorem to find the length of the missing side.

\(\displaystyle x^2+6^2=10^2\)

\(\displaystyle x^2+36=100\)

\(\displaystyle x^2=64\)

\(\displaystyle x=\sqrt{64}=8\)

Example Question #14 : Right Triangles

Find the length of the missing side.

6

Possible Answers:

\(\displaystyle 300\)

\(\displaystyle 20\)

\(\displaystyle 10\sqrt3\)

\(\displaystyle 10\sqrt5\)

Correct answer:

\(\displaystyle 10\sqrt3\)

Explanation:

Use the Pythagorean Theorem to find the length of the missing side.

\(\displaystyle x^2+10^2=20^2\)

\(\displaystyle x^2+100=400\)

\(\displaystyle x^2=300\)

\(\displaystyle x=\sqrt{300}=10\sqrt{3}\)

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