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

Lesson 3: Lesson 4: Proportional relationships and equations

# Constant of proportionality from table (with equations)

Sal identifies the constant of proportionality from table.

## Want to join the conversation?

• For a proportionality, do you always find the ratio from the left to the right, or in some cases do you find the ratio from right to left, and if you do, how do you know which direction you take the ratio from in a problem(left to right or right to left)
• so from left to right in most cases is is multiplication but right to left in most cases in division.
• so when your doing the table do you always times by 2.5
• No if the constant of proportionality is 2.5 then you do
• he just took 2.5 out of nowhere like what
• It doesn't come out of nowhere. As Sal tells you in the video, you start with the value of "x" and you find the value that you can multiply with "x" to create the y-value.

Or, use the forumula: y=rx
If x=4 and y=10, plug in those values: 10=4r
Solve for "r" by dividing by 4: r = 10/4 = 2.5

Hope this helps.
• so basically, you have to find a specific number to solve for each problem with the same number?
• yes but that specific number is called the constant of proportionality and its what fits the entire question together
• what if the numbers on the right are fractions
• thi is to hard for my tiny brain lol
• But what if "y" is a mixed number? Would you convert it to a fraction and then try to make it into a decimal? I'm confused :/
• To turn a mixed number into a decimal without turning it into an improper fraction, all you have to do is:

For example we have a mixed number:
3 4/5

Take the whole number from the fraction which is 3, and then solve the fraction:
4/5 = 0.8

Add the result to the whole number and there you have it:
3 + 0.8 = 3.8
• I still have a bit of trouble with this, but I'm pretty sure that's just because of my very miniscule brain.
• you do not have a miniscule brain everyone has a perfect sized brain you just have to apply yourself and put what you learned in your (what I like to call) memory banks
• where did yogurt 21/2?