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# 3 Easy Steps for Answering What are Supplementary Angles?

Get the free Supplementary Angles worksheet and other resources for teaching & understanding what are Supplementary Angles

## Here’s how to find Supplementary Angles

Supplementary Angles are two angles whose sum is 180 degrees. This means that when two angles are added together and their sum is 180 degrees then they are Supplementary Angles. You can find out if angles are Supplementary Angles by using addition or subtraction. When determining which angles what are Supplementary Angles, you subtract the angle you know from 180 degrees to get the missing angle measure. For example, if you know one angle measure is 60 degrees and you need to find out the second angle measure, you can do 180 degrees subtracted by 60 degrees to get the remaining angle measure of 130.

Common Core Standard: 7.G.5
Return To: Home, 7th Grade

## The Complete Supplementary Angles Definition

Well what do supplementary angles add up to anyway? When two angles add up to 180 degrees they are called Supplementary Angles. You can tell whether or not angles are are Supplementary Angles by utilizing subtraction or addition. To answer how to find Supplementary Angles, you subtract to get any missing angle measure from 180 degrees. For instance, in the event that you know one angle measure is 125 degrees and you have to discover the second angle measure, you do 180 degrees subtracted by 125 degrees to get the last angle measure of 55 degrees.

## 3 Steps to Answer any Supplementary Angles Example Problem

1. Supplementary Angles are two angles that add up to 180 degrees.
2. If you know one angle measure, you subtract it from 180 degrees to get the other angle measure.
3. You can check to make sure angles are Supplementary by making sure the angles form a straight line.

## Finding Supplementary Angles Practice Problems Quiz

/5

Supplementary Angles Quiz

Click Start to begin the practice quiz!

1 / 5

Find the value of x.

2 / 5

Find the value of x.

3 / 5

Find the value of x.

4 / 5

Find the value of x.

5 / 5

Find the value of x.

Your score is

0%

## Watch the video explanation of our Supplementary Angles worksheet

Watch our free video on do Supplementary Angles add up to 180. This video shows how to solve problems that are on our free Supplementary Angles worksheets that you can get by submitting your email above.

Watch the free Supplementary Angles video on YouTube here: Supplementary Angles Video

Video Transcript:

This video is about answering the question what are supplementary angles. You can get this finding supplementary angle worksheet for free by clicking on the link in the description below.

The first thing we need to talk about is what are supplementary angles and what is the definition of supplementary angles? The supplementary angles definition is when you have two angles that are added together to get 180 degrees. 180 degrees is just a straight line. IN this example at the bottom, we have a straight line. You can see that there is a ray coming off of the straight like to create two angles. If you look, we already know that this angle here is 50 degree, but we don’t know how many degrees the second angle is. We do know that supplementary angles are 180 degree. We know that one angle is 50 degrees so we know that we can do 180 degrees minus 50 degrees to get the missing angle. This missing angle has to be 130 degrees because the two angles together have to add up to 180 degrees. So if one supplementary angle is 50 degrees then the second supplementary angle has to be 130 degrees because the two added together have to add up to 180 degrees.

Let’s do a couple practice problems on our supplementary angles worksheet. We already know that the supplementary angle definition is that when one angle plus a second angle add up to 180 degrees. We already know that a straight line is equal to 180 degrees. In the case of number one, we know the first angle is 135 and we know that both angles have to add up to 180 degrees because they form a straight line. We know that both angles together have to add up to 180 degree. So we are going to take 180 degrees and subtract it from the angle that we know which is 135 degrees. When you subtract 180 minus 135 you get 45 degrees as the difference. Which means that this missing angle has to be 45 degrees because the two added together have to add up to 180 because they are supplementary.

Jumping down to number two on our supplementary angles examples. Again, the definition of supplementary angles is that when one angle plus a second angle adds up to 180 degrees. We know that this angle here is 128 and we know that this line had to equal 180 degrees total. So we know that the missing angle has to be the difference between 180 degrees and 128 degrees. You do 180 degrees subtracted by 128 degrees to get the difference of 52 degrees. Now we know that this angle has to be 52 degrees.

The last question that were going to do on our supplementary angles examples is number 5. Again, we know that supplementary angles definition is that when two angles add up to 180 degrees. This problem gives us one angle that is 45 degrees and an ingle that we don’t know. But we do know that a straight line adds up to 180 degrees. To get the missing angle were going to do 180 degrees minus the angle that we do know, which is 45 degrees. We get the answer of 135 degrees. So, the missing angle is 135 degrees.

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