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

You only use the constant of proportionality that is given in the table.It varies in each problem.

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

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

Proportional means it changes rate at a constant rate right?

Proportional means that the ratio of y to x is constant. This means that whenever x is multiplied by a factor, then y is multiplied by the same factor. Have a blessed, wonderful day!

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Constant of proportionality from table (with equations)

Name: Constant of proportionality from table (with equations)
Uploaded: 2017-11-14T23:43:55Z
Description: Sal identifies the constant of proportionality from table.

CCSS.Math:

7.RP.A.2

7.RP.A.2b

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Sal identifies the constant of proportionality from table.

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finleyc
Posted 5 years ago. Direct link to finleyc's post “so when your doing the ta...”
so when your doing the table do you always times by 2.5
Button navigates to signup pageComment on finleyc's post “so when your doing the ta...”
(20 votes)
Answer
- BusinessMan
  Posted 5 years ago. Direct link to BusinessMan's post “You only use the constant...”
  You only use the constant of proportionality that is given in the table.It varies in each problem.
  Comment on BusinessMan's post “You only use the constant...”
  (25 votes)
4804140469
Posted 5 years ago. Direct link to 4804140469's post “For a proportionality, do...”
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)
Button navigates to signup pageComment on 4804140469's post “For a proportionality, do...”
(24 votes)
Answer
- 3.141592653589793
  Posted a year ago. Direct link to 3.141592653589793's post “so from left to right in ...”
  so from left to right in most cases is is multiplication but right to left in most cases in division.
  Comment on 3.141592653589793's post “so from left to right in ...”
  (4 votes)
dmora19
Posted 3 years ago. Direct link to dmora19's post “he just took 2.5 out of n...”
he just took 2.5 out of nowhere like what
Button navigates to signup pageComment on dmora19's post “he just took 2.5 out of n...”
(10 votes)
Answer
- Kim Seidel
  Posted 3 years ago. Direct link to Kim Seidel's post “It doesn't come out of no...”
  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.
  Comment on Kim Seidel's post “It doesn't come out of no...”
  (19 votes)
William Stevenson
Posted 5 years ago. Direct link to William Stevenson's post “so basically, you have to...”
so basically, you have to find a specific number to solve for each problem with the same number?
Button navigates to signup pageComment on William Stevenson's post “so basically, you have to...”
(10 votes)
Answer
- 3.141592653589793
  Posted a year ago. Direct link to 3.141592653589793's post “yes but that specific num...”
  yes but that specific number is called the constant of proportionality and its what fits the entire question together
  Button navigates to signup page
  (2 votes)
Yepez, Juan
Posted 5 years ago. Direct link to Yepez, Juan's post “what if the numbers on th...”
what if the numbers on the right are fractions
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(10 votes)
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jeremy.nantel
Posted 3 years ago. Direct link to jeremy.nantel's post “thi is to hard for my tin...”
thi is to hard for my tiny brain lol
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Luke
Posted 6 months ago. Direct link to Luke's post “I willl ask a question! C...”
I willl ask a question! Can this comment get to at least 1 real vote?
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(7 votes)
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EHPhillips333
Posted 4 years ago. Direct link to EHPhillips333's post “But what if "y" is a mixe...”
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 :/
Button navigates to signup pageComment on EHPhillips333's post “But what if "y" is a mixe...”
(5 votes)
Answer
- Arzal
  Posted 3 years ago. Direct link to Arzal's post “To turn a mixed number in...”
  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
  Comment on Arzal's post “To turn a mixed number in...”
  (4 votes)
MemeVee
Posted 3 years ago. Direct link to MemeVee's post “I still have a bit of tro...”
I still have a bit of trouble with this, but I'm pretty sure that's just because of my very miniscule brain.
Button navigates to signup pageComment on MemeVee's post “I still have a bit of tro...”
(6 votes)
Answer
- 3.141592653589793
  Posted a year ago. Direct link to 3.141592653589793's post “you do not have a miniscu...”
  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
  Button navigates to signup page
  (1 vote)
Awesomeorigamifolder
Posted 2 years ago. Direct link to Awesomeorigamifolder's post “Proportional means it cha...”
Proportional means it changes rate at a constant rate right?
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(2 votes)
Answer
- Ian Pulizzotto
  Posted 2 years ago. Direct link to Ian Pulizzotto's post “Proportional means that t...”
  Proportional means that the ratio of y to x is constant. This means that whenever x is multiplied by a factor, then y is multiplied by the same factor.
  
  Have a blessed, wonderful day!
  Button navigates to signup page
  (5 votes)

Video transcript

- [Instructor] We're told the quantities x and y are proportional, and then they give us a table where they give us a bunch of x's and they give us the corresponding y's. When x is four, y is 10. When x is five, y is 12.5, and so on and so forth. Find the constant of proportionality, r, in the equation y is equal to r times x. So pause this video and see if you can figure that out. All right so we wanna find the constant, the constant of proportionality, I sometimes have trouble saying that, r, where if I for any x, if I multiply it by r I get y. Well we just have to look at each of these x's and figure out well what are we multiplying by to get to y. So what do I have to multiply four by to get to 10? Well if you multiply it by 10/4, if you multiply it by 10/4, then you're gonna get to 10. And 10/4 is the same thing as multiplying it by, let's see that is 2 1/2. So this is times 2 1/2. So let's see does that hold? In every case if I multiply by 2 1/2, if I multiply x by 2 1/2, do I get y? So five times 2 1/2, five times two is 10, and then another 1/2 is 2.5. It indeed does equals 12.5. Five times 2.5. And then here 10 times 2.5 is clearly 25. And you can work it out by hand. I did the little bit of the multiplication in my head, but you can see in every case, I take my x, I multiply it by 2.5, I get my y. So in every case I take my x and multiply it by the constant of proportionality 2.5, I get my y. So what's the constant of proportionality? It is 2.5.

7th grade

Course: 7th grade > Unit 4

Constant of proportionality from table (with equations)

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Video transcript