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### Course: 8th grade (Illustrative Mathematics)>Unit 3

Lesson 2: Lesson 4: Comparing proportional relationships

# Rates & proportional relationships example

Let's compare unit rates in equations and graphs. Learn how a change in 'x' affects 'y' in an equation like y = 6.5x, and see how this compares to the rate of change in a graph. Uncover why one might increase at a slower pace than the other. Created by Sal Khan.

## Want to join the conversation?

• This is very confusing. can someone explain it?
(38 votes)
• You will have to be more specific find the spot in the video and ask about that part.
(3 votes)
• what does ambiguous mean
(11 votes)
• Ambiguous means unclear or having multiple meanings. You 𝘤𝘢𝘯 look it up.
(17 votes)
• anyone else not get this?
(17 votes)
• Yes! I don't understand well, too.
(2 votes)
• im just so confused i don't understand very well
(10 votes)
• How would you do it if it was,

A giraffe grows 3-10 inches per day,

Which of the following equations, where t represents time in days, and H represents height in centimeters, could be descriptions of the growth of the giraffes height?

H=1.1t
H=2.5t
H=7.1t
H=9.3t

Thanks for helping me!
(5 votes)
• So you said that the giraffe grows between 3-10 cm a day..
Where t = days an h = height.

So there can be more than one answer because we don’t how how much exactly it grows..
So the answers would be between 3 and 10.
3) H = 7.1t
4) H = 9.3t
Those were the only 2 possible answers in the given options..

Hope this helped
(8 votes)
• This makes no sense please help
(4 votes)
• So in the video the question is, "is y=6.5x a slower unit rate (the unit rate is 6.5)then the unit rate shown in the graph. The graphs unit rate is y=3.5x (where 3.5 is the unit rate). So if you compare the two unit rates, 6.5(sentence unit rate) and 3.5(graph unit rate), 3.5 is the slower unit rate. Hope this helps :}
(10 votes)
• What if all of the rates are not equal would the answer still be the smae?
(6 votes)
• It depends on the rates
(4 votes)
• I don't get this. Can someone please help me?
(4 votes)
• I can only help you if you tell me what you don't understand.
(6 votes)
• You use the Show solution?
(6 votes)
• But what if In the problem it is like this 17,000 compared to the for example(3,6) What do we do?
(3 votes)
• Please elaborate
(6 votes)

## Video transcript

Which is less-- the unit rate of the equation y equals 6.5x or the unit rate of the graph shown below? So when they're talking about unit rate-- and they're actually a little bit ambiguous here. They should have been clearer in this question. I'm assuming they're asking us about the unit rate at which y changes with respect to x. Or how much does y change for a change of 1 in x, the unit rate. And over here, you see when x changes 1, y is going to change by 6.5. Every time x increases by 1, y is going to increase by 6.5. Or you could say the unit rate of change of y with respect to x is 6.5 for every 1 change in x. In this graph right over here, as x changes 1, as x increases 1, y increases it looks like by about 3 and 1/2. x increases by 1, y increases by 3 and 1/2. So the unit rate of change here of y with respect to x is 3 and 1/2 for every unit increase in x. So this line is increasing at a slower rate than this equation. Or y in this line is increasing at a slower rate with respect to x than y is increasing with respect to x in this equation right over here. So the unit rate of the graph is less than the unit rate of the equation.