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## SAT

### Course: SAT > Unit 10

Lesson 3: Problem solving and data analysis- Ratios, rates, and proportions — Basic example
- Ratios, rates, and proportions — Harder example
- Percents — Basic example
- Percents — Harder example
- Units — Basic example
- Units — Harder example
- Table data — Basic example
- Table data — Harder example
- Scatterplots — Basic example
- Scatterplots — Harder example
- Key features of graphs — Basic example
- Key features of graphs — Harder example
- Linear and exponential growth — Basic example
- Linear and exponential growth — Harder example
- Data inferences — Basic example
- Data inferences — Harder example
- Center, spread, and shape of distributions — Basic example
- Center, spread, and shape of distributions — Harder example
- Data collection and conclusions — Basic example
- Data collection and conclusions — Harder example

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# Key features of graphs — Harder example

Watch Sal work through a harder Key features of graphs problem.

## Want to join the conversation?

- the question asks for rate of change of altitude, then why do we calculate rate of change of altitude over rate of change of time??(3 votes)
- because the answers is in altitude per second, so you have to know how many seconds passed.(5 votes)

- what kind of refrigerator was that? Did that guy bought it on wish or what, after 2 hours and the dish is at 40 degrees Fahrenheit, what?, I am joking(3 votes)
- lol

i was thinking the same thing(1 vote)

- I get it how you got the answer, but why did you do altitude/time wouldn't that be y/x and in math you are suppose to do x/y so would it be 28/26 = 1.07692308, and then round to 1.08. So wouldn't the answer be the choice "B"?(3 votes)
- Pls has the June 3rd SAT been posponed(1 vote)
- Depends on where you live but I don't believe so ;)

You can do this!(1 vote)

- the video is really nice but there are some median questions asked in the same lesson and there isnt a video that explain them(0 votes)
- They are asking that they are trying it get the rate u guys(0 votes)

## Video transcript

- [Instructor] Ruby
puts a dish of macaroni and cheese into the regrigerator. The dish was 80, 80 degrees
Fahrenheit when she put it in. And the inside of the refrigerator was 40 degrees Fahrenheit. The dish cooled quickly at first, so this is gonna be
interesting, quickly at first, then slowed as it
approached the temperature inside the refrigerator, all right. Which of the following
graphs in the mT-plane could best represent the temperature T, in degrees Fahrenheit,
m minutes after Ruby put the dish in the refrigerator? So mT-plane sounds very fancy,
but all they're saying is is the horizontal axis,
that's our time axis, and it's gonna be measured
in minutes, m for minutes. And our vertical axis in this plane, in this coordinate plane, is going to be our temperature axis, and it's measured in Fahrenheit degrees. So let's see what they're saying. So the dish started at 80, at 80 degrees, at 80 degrees Fahrenheit. So at zero minutes, right when she put it into the fridge, it should be 80 degrees. So this one right over here, this one is indeed at 80 degrees. This graph right over
here, this is starting at zero degrees, not at, it
needs to start at 80 degrees if we're gonna model
what actually happened. So this, we can rule
that one out immediately. Then when you look at these choices, this one's starting at 40 degrees. Once again, not what we need. We need it to start at 80
degrees at zero minutes, so we'll rule that one out. This one also starts at 80 degrees. Now let's think about the shape of what the curve should be. They say the dish cooled quickly at first, then slowed, then slowed, as it approached the temperature inside the refrigerator. Now, does this graph describe that? It starts, before it
was in the refrigerator it was at 80 degrees, or
right when they put it in the refrigerator, it's at 80 degrees. And then it starts, its
temperature declines quickly at first, but then
the rate of decline slows as it approaches the temperature
inside of the fridge, that 40 degrees, and that seems like that this is what's happening. It's becoming, the slope is becoming, it starts out quite
negative, but it becomes less and less and less negative as we get closer and closer
to the 40 degrees Fahrenheit. This one over here, after
some number of minutes, we do end up at this
40 degrees Fahrenheit. But the rate of decline is
constant the entire time. This is a line, this is describing a constant rate of decline. But what they described is
a changing rate of decline. The dish cooled quickly at first. So that would be a steep
decline, cooled quickly at first, then slowed as it
approached the temperature inside the refrigerator. So the decline slows,
it becomes less negative as we approach the temperature
of the refrigerator. So you have this change in the
rate of temperature change. And so you are going
to, or at least I would, pick this one right over here. This one right over here
describes a constant rate, which is not what was
described in the question.