ACT Math : How to find the length of the hypotenuse of a right triangle : Pythagorean Theorem

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #21 : How To Find The Length Of The Hypotenuse Of A Right Triangle : Pythagorean Theorem

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Given the right triangle in the diagram, what is the length of the hypotenuse?

 

Possible Answers:

\(\displaystyle 7\ in\)

\(\displaystyle 12\ in\)

\(\displaystyle 20\ in\)

\(\displaystyle 14\ in\)

\(\displaystyle 10\ in\)

Correct answer:

\(\displaystyle 10\ in\)

Explanation:

To find the length of the hypotenuse use the Pythagorean Theorem: \(\displaystyle a^{2}+b^{2}=c^{2}\)

 Where \(\displaystyle a\) and \(\displaystyle b\) are the legs of the triangle, and \(\displaystyle c\) is the hypotenuse.

\(\displaystyle 6^{2}+8^{2}=100\)

\(\displaystyle (100)^{\frac{1}2}=10\)

The hypotenuse is 10 inches long.

 

Example Question #11 : Apply The Pythagorean Theorem To Determine Unknown Side Lengths In Right Triangles: Ccss.Math.Content.8.G.B.7

Righttriangle

Triangle ABC is a right triangle. If the length of side A = 3 inches and C = 5 inches, what is the length of side B?  

Possible Answers:

6 inches

1/2 inches

1 inches

4 inches

4.5 inches

Correct answer:

4 inches

Explanation:

Using the Pythagorean Theorem, we know that \(\displaystyle a^{2} + b^{2} = c^{2}\).

This gives: 

\(\displaystyle 3^{2} + b^{2} = 5^{2}\)

\(\displaystyle 9 + b^{2} = 25\)

Subtracting 9 from both sides of the equation gives: 

\(\displaystyle b^{2} = 16\)

\(\displaystyle b = 4\) inches

 

Righttriangle

Example Question #51 : Right Triangles

Righttriangle

Triangle ABC is a right triangle. If the length of side A = 8 inches and B = 11 inches, find the length of the hypoteneuse (to the nearest tenth). 

Possible Answers:

184 inches

14.2 inches

185 inches

13.7 inches

13.6 inches

Correct answer:

13.6 inches

Explanation:

Using the Pythagrean Theorem, we know that \(\displaystyle a^{2} + b^{2} = c^{2}\).

This tells us:

\(\displaystyle 8^{2} + 11^{2} = C^{2}\)

\(\displaystyle 64 + 121 = C^{2}\)

\(\displaystyle 185 = C^{2}\)

Taking the square root of both sides, we find that \(\displaystyle C = 13.6\) inches

Example Question #64 : Geometry

Righttriangle

Given:

A = 6 feet

B = 9 feet

What is the length of the hypoteneuse of the triangle (to the nearest tenth)?

Possible Answers:

10.2 feet

10.8 feet

10.6 feet

10.5 feet

10.1 feet

Correct answer:

10.8 feet

Explanation:

Using the Pythagrean Theorem, we know that \(\displaystyle a^{2} + b^{2} = c^{2}\).

This tells us:

\(\displaystyle 6^{2} + 9^{2} = C^{2}\)

\(\displaystyle 36 + 81 = C^{2}\)

\(\displaystyle 117 = C^{2}\)

Taking the square root of both sides, we find that \(\displaystyle C = 10.8\)

Example Question #61 : Geometry

Righttriangle

Given:

A = 2 miles

B = 3 miles

What is the length of the hypoteneuse of triangle ABC, to the nearest tenth? 

Possible Answers:

3.5 miles

3.2 miles

3.7 miles

3.4 miles

3.6 miles

Correct answer:

3.6 miles

Explanation:

Using the Pythagrean Theorem, we know that \(\displaystyle a^{2} + b^{2} = c^{2}\).

This tells us:

\(\displaystyle 2^{2} + 3^{2} = C^{2}\)

\(\displaystyle 4 + 9 = C^{2}\)

\(\displaystyle 13 = C^{2}\)

Taking the square root of both sides, we find that \(\displaystyle C = 3.6\)

Example Question #71 : Geometry

Given that two sides of a right triangle measure 2 feet and 3 feet, respectively, with a hypoteneuse of x, what is the perimeter of this right triangle (to the nearest tenth)?

Possible Answers:

9.4 feet

18 feet

6.4 feet

8.6 feet

3.6 feet

Correct answer:

8.6 feet

Explanation:

Using the Pythagrean Theorem, we know that \(\displaystyle a^{2} + b^{2} = c^{2}\).

This tells us:

\(\displaystyle 2^{2} + 3^{2} = C^{2}\)

\(\displaystyle 4 + 9 = C^{2}\)

\(\displaystyle 13 = C^{2}\)

Taking the square root of both sides, we find that \(\displaystyle C = 3.6\)

To find the perimeter, we add the side lengths together, which gives us that the perimeter is: \(\displaystyle 3 + 2 + 3.6 = 8.6\)

Example Question #52 : Right Triangles

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\(\displaystyle In\;\Delta GHJ, \;what\;is\;the\;length\;of\;\overline{GJ}?\)

Possible Answers:

\(\displaystyle 10\)

\(\displaystyle 13\)

\(\displaystyle 12\)

\(\displaystyle 5\)

Correct answer:

\(\displaystyle 13\)

Explanation:

\(\displaystyle Use\;the\;Pythagorean\;Theorem:A^2+B^2=C^2,\;to\; find\;\overline{GJ}.\)

\(\displaystyle 5^2+12^2=C^2\)

\(\displaystyle 25+144=C^2\)

\(\displaystyle 169=C^2\)

\(\displaystyle C=\sqrt{169}=13\)

Example Question #21 : How To Find The Length Of The Hypotenuse Of A Right Triangle : Pythagorean Theorem

Kathy and Jill are travelling from their home to the same destination. Kathy travels due east and then after travelling 6 miles turns and travels 8 miles due north. Jill travels directly from her home to the destination. How miles does Jill travel? 

Possible Answers:

\dpi{100} \small 10\ miles\(\displaystyle \dpi{100} \small 10\ miles\)

\dpi{100} \small 14\ miles\(\displaystyle \dpi{100} \small 14\ miles\)

\dpi{100} \small 12\ miles\(\displaystyle \dpi{100} \small 12\ miles\)

\dpi{100} \small 8\ miles\(\displaystyle \dpi{100} \small 8\ miles\)

\dpi{100} \small 16\ miles\(\displaystyle \dpi{100} \small 16\ miles\)

Correct answer:

\dpi{100} \small 10\ miles\(\displaystyle \dpi{100} \small 10\ miles\)

Explanation:

Kathy's path traces the outline of a right triangle with legs of 6 and 8. By using the Pythagorean Theorem

  \dpi{100} \small 6^{2}+8^{2}=x^{2}\(\displaystyle \dpi{100} \small 6^{2}+8^{2}=x^{2}\)

\dpi{100} \small 36+64=x^{2}\(\displaystyle \dpi{100} \small 36+64=x^{2}\) 

\dpi{100} \small x=10\(\displaystyle \dpi{100} \small x=10\) miles

Example Question #51 : Right Triangles

\(\displaystyle Which\; of \;the \;following \;is\; NOT\; true\; about \;the \;hypotenuse \;of \;a\; triangle?\)

Possible Answers:

\(\displaystyle It\;is\;the\;longest\;side.\)

\(\displaystyle It\;is\;always\;greater\;than\;1.\)

\(\displaystyle It\;is\;across\;from\;the\;right\;angle.\)

\(\displaystyle It\;is\;always\;across\;from\;the\;largest\;angle\;in\;the\;triangle.\)

Correct answer:

\(\displaystyle It\;is\;always\;greater\;than\;1.\)

Explanation:

\(\displaystyle The\;hypotenuse\;can\;be\;between\;0\;and\;1.\)

Example Question #31 : How To Find The Length Of The Hypotenuse Of A Right Triangle : Pythagorean Theorem

In order to get to work, Jeff leaves home and drives 4 miles due north, then 3 miles due east, followed by 6 miles due north and, finally, 7 miles due east.  What is the straight line distance from Jeff’s work to his home?

 

 

Possible Answers:

15

11

6√2

2√5

10√2

Correct answer:

10√2

Explanation:

Jeff drives a total of 10 miles north and 10 miles east.  Using the Pythagorean theorem (a2+b2=c2), the direct route from Jeff’s home to his work can be calculated.  102+102=c2.  200=c2. √200=c. √100Ÿ√2=c. 10√2=c

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