High School Math : Triangles

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #4 : Right Triangles

Which set of sides could make a right triangle?

Possible Answers:

6, 7, 8

4, 6, 9

10, 12, 16

9, 12, 15

Correct answer:

9, 12, 15

Explanation:

By virtue of the Pythagorean Theorem, in a right triangle the sum of the squares of the smaller two sides equals the square of the largest side. Only 9, 12, and 15 fit this rule.

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

A right triangle with a base of 12 and hypotenuse of 15 is shown below. Find x.

Screen_shot_2013-03-18_at_10.29.39_pm

Possible Answers:

3.5

4

5.5

5

4.5

Correct answer:

4

Explanation:

Using the Pythagorean Theorem, the height of the right triangle is found to be = √(〖15〗–〖12〗2) = 9, so x=9 – 5=4

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

A right triangle has sides of 36 and 39(hypotenuse).  Find the length of the third side

Possible Answers:

33√2

42

33

15

12 √6

Correct answer:

15

Explanation:

use the pythagorean theorem:

a2 + b2 = c2  ; a and b are sides, c is the hypotenuse

a2 + 1296 = 1521

a2 = 225

a = 15

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

Bob the Helicopter is at 30,000 ft. above sea level, and as viewed on a map his airport is 40,000 ft. away. If Bob travels in a straight line to his airport at 250 feet per second, how many minutes will it take him to arrive?

Possible Answers:

2 hours and 30 minutes

4 hours and 0 minutes

3 minutes and 50 seconds

1 hour and 45 minutes

3 minutes and 20 seconds

Correct answer:

3 minutes and 20 seconds

Explanation:

Draw a right triangle with a height of 30,000 ft. and a base of 40,000 ft. The hypotenuse, or distance travelled, is then 50,000ft using the Pythagorean Theorem. Then dividing distance by speed will give us time, which is 200 seconds, or 3 minutes and 20 seconds.

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

A right triangle has two sides, 9 and x, and a hypotenuse of 15. What is x?

Possible Answers:

10

14

13

12

11

Correct answer:

12

Explanation:

We can use the Pythagorean Theorem to solve for x.

92 + x2 = 152

81 + x2 = 225

x2 = 144

x = 12

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

The area of a right traingle is 42. One of the legs has a length of 12. What is the length of the other leg?

Possible Answers:

7\displaystyle 7

11\displaystyle 11

9\displaystyle 9

6\displaystyle 6

5\displaystyle 5

Correct answer:

7\displaystyle 7

Explanation:

Area= \frac{1}{2}\times base\times height\displaystyle Area= \frac{1}{2}\times base\times height

42=\frac{1}{2}\times base\times 12\displaystyle 42=\frac{1}{2}\times base\times 12

42=6\times base\displaystyle 42=6\times base

base=7\displaystyle base=7

Example Question #141 : Plane Geometry

Triangle

If \displaystyle \angle A=30^{\circ} and \displaystyle \overline{AB}=4, what is the length of \displaystyle \overline{BC}?

Possible Answers:

\displaystyle 4

\displaystyle \frac{4\sqrt{3}}{3}

\displaystyle 3

\displaystyle \frac{4}{3}

Correct answer:

\displaystyle \frac{4\sqrt{3}}{3}

Explanation:

AB is the leg adjacent to Angle A and BC is the leg opposite Angle A.

Since we have a \displaystyle 30^{\circ}-60^{\circ}-90^{\circ} triangle, the opposites sides of those angles will be in the ratio \displaystyle x-x\sqrt{3}-2x.

Here, we know the side opposite the sixty degree angle. Thus, we can set that value equal to \displaystyle x\sqrt{3}.

\displaystyle 4=x\sqrt{3}

\displaystyle \frac{4}{\sqrt{3}}=\frac{x\sqrt{3}}{\sqrt{3}}

\displaystyle \frac{4}{\sqrt{3}}\cdot \frac{\sqrt{3}}{\sqrt{3}}=x

\displaystyle x=\frac{4\sqrt{3}}{3}

which also means

\displaystyle \overline{BC}=\frac{4\sqrt{3}}{3}

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

Solve for x.

Possible Answers:

2

7

6

12

Correct answer:

6

Explanation:

Use the Pythagorean Theorem. Let a = 8 and = 10 (because it is the hypotenuse)

\small a^2+x^2=c^2\displaystyle \small a^2+x^2=c^2

\small 8^2+x^2=10^2\displaystyle \small 8^2+x^2=10^2

\small 64+x^2=100\displaystyle \small 64+x^2=100

\small x^2=100-64=36\displaystyle \small x^2=100-64=36

\small x=6\displaystyle \small x=6

Example Question #21 : Right Triangles

Solve for \displaystyle \small x.

Question_1

Possible Answers:

\displaystyle 3

\displaystyle 19

\displaystyle 9

\displaystyle 20

Correct answer:

\displaystyle 9

Explanation:

Use the Pythagorean Theorem to solve for the missing side of the right triangle.

\displaystyle a^2+b^2=c^2

In this triangle, \displaystyle \small a=x,\ b=12,\ c=15.

\displaystyle x^2+12^2=15^2

Now we can solve for \displaystyle \small x.

\displaystyle x^2+144=225

\displaystyle x^2=81

\displaystyle x=9

Example Question #21 : Right Triangles

Solve for \displaystyle \small x.

Question_9

Possible Answers:

\displaystyle 110

\displaystyle 110\sqrt2

\displaystyle 55\sqrt2

\displaystyle 110\sqrt3

Correct answer:

\displaystyle 110

Explanation:

This image depicts a 30-60-90 right triangle. The length of the side opposite the smallest angle is half the length of the hypotenuse.

\displaystyle a^2+b^2=c^2\rightarrow (a)^2+(a\sqrt{3})^2=(2a)^2

\displaystyle 2a=220

\displaystyle a=\frac{220}{2}=110

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