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### Course: Algebra 2>Unit 12

Lesson 4: Modeling with two variables

# Graph labels and scales

When graphing a real-world relationship, we need to pick labels and axis scales that are appropriate for the purpose of our model. Created by Sal Khan.

## Want to join the conversation?

• to me i see no way you could use it like this in everyday life except, possibly your job
• This will be very important in certain jobs, but you could use it in everyday life too. If you want to compare certain teams and their wins, you might need to use this. This is useful.
• I have another problem that I can't figure out. It goes like this:
Ashley is doing some math exercises on a website called Khan Academy. In Khan Academy, you have to get at least 70% of the problems in an exercise right in order to gain proficiency.
So far, Ashley has answered correctly 3 out of 7 times. Suppose she answers all of the following q questions correctly and gains proficiency in the exercise.
Write an inequality in terms of q that models the situation.

None of it makes sense to me. How are you supposed to do this problem?
• Let q = questions answered correctly

Key Terms:
- At least get 70%
- Assume Ashley solves all of the questions correctly after answering 3

"at least 70% of the problems in an exercise right"
Translated: .7 <= [expression]

"So far, Ashley has answered correctly 3 out of 7 times." and "Suppose she answers all of the following q questions correctly and gains proficiency in the exercise."
Ashley already got 3/7 correct ! Excellent, and now she solved q questions correctly.

Imagine this:
[correct questions]/[total questions]
Correct questions would be 3+q
Total questions would be 7+q, because we don't know how many questions she answered ! We just know that she answered q questions correctly after getting 3 questions correct.

Our inequality now is:

.7 <= (3+q)/(7+q)
hopefully that helps !
• How did Chloe model her graph as P=20-25*(0.8)^t? How did she derive (0.8)^t? And why didn't she derive P= 0-25 degrees instead of 20-25? I'm just curious how to use these parameters sometime for my own experiment.

• Unfortunately, this is just a model non-representative with real life for the sake of explaining exponential models. However though in exponential equations:
a(b)^x+c

a = Initial Value
b = Constant trend growth/decay
x = Time (determined by how you define it
c = Horizontal Asymptote (as you increase x, the output will level out to this value