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### Course: 7th grade (Illustrative Mathematics)>Unit 2

Lesson 3: Lesson 4: Proportional relationships and equations

# Equations for proportional relationships

Learn how to write a proportional equation y=kx where k is the so-called "constant of proportionality".

## Want to join the conversation?

• So I am doing the practice problems for this right now and sometimes the constant of proportionality is a fraction, like "y=1/3x" but sometimes it is a number or a decimal, like "y=0.34x" or "y=4x". How do I know which one to do? There have been multiple times where I put the decimal equal to the fraction, like 0.33 for 1/3 and gotten it wrong because it was supposed to be the fraction (and vice versa)
• I have experienced similar issues entering answers. After doing quite a few of these types of problems, I have found that entering your answer as a fraction is the safer bet, especially when your answer is something like 10/7x=y as 10/7 is a repeating decimal. I enter the answer as a decimal only if the question prompts me to do something like "round my answer to the nearest hundredth." Then I obviously know my answer should have a decimal in it. Otherwise, I just seem to run into problems with entering them usually do to rounding.

So yeah, I just feel that it is better to answer these kinds of questions with a fraction instead of the decimal unless you are specifically told to do so in the question.
• i dont understand this
• what he is trying to say when 4 and 1 I think they mean the unit rate is 4 or it can 4/1
• This video taught me what my math teacher has been trying to teach my class for half a month now in the span of 1 minute and 18 seconds. Thanks Khan Academy.
• ?? does this mean in real life ?_?
• what is real life example of the equation y=1/20*x
• i have a question, how is 8/2 and 12/3 equal to 4
• Just remember that when there is a fraction, it basically means you're dividing. So 8/2 is 8 divided by 2, which equals 4. 12/3 is 12 divided by 3, which equals 4.
• how to turn a slope-intercept equation into a proportional equation
• the video doesn't show how to get a decimal from the graph
• I don't understand the part with the table can someone help
(1 vote)
• The table is basically a representation of what y or x is equal to once you multiply it by the proportionality constant. if our equation was y=2x, if x is 1 we can say y=2*1 or y=2. if x is 2 then y=2*2 or y=4 and so on and so forth.
I hope this helps :)
x|y
1|2
2|4
3|6
4|8
5|10