Main content

## 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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# Percents — Basic example

Watch Sal work through a basic Percents problem.

## Want to join the conversation?

- 2:56, how did he end up with 20%? I don't understand why its 20%(15 votes)
- the total was 100 %

but , 22.40/28 = 0.8 or 80%

we paid only 80% of it , so 100 - 80 = 20 %

hope you get it ! :)(30 votes)

- if you have questions like this how do you know if you should answer the question using these steps if there are questions worded or phrased differently(6 votes)
- The best way you can identify a problem like this is if it assumes the starting point is 100%. Like Sal had said, if you are starting from a whole and consistently subtracting the same amount every time, you don't even need to think about the percentages, you can just substitute them as units.(1 vote)

- why did he multiplied with 0.7(3 votes)
- Hello Sebnem,

The discount was 30% but we still need to pay the other 70%.

Sal does the same thing again when we pay 80% at the counter. Therefore the additional discount was 20%.

Regards,

APD(10 votes)

- At1:15why does Sal divide 22.40 by 28?(4 votes)
- Sal divides 22.40 by 28 to figure out what percent of the already discounted price was paid.

With that information, he could find out what the additional discount was.(6 votes)

- Im having a quiz tomorrow on Ratios, Rates, Proportions, Percents and Units. Which one should i study first?(0 votes)
- Everything because you don't want to fail.(16 votes)

- As per Sal's percentage based solution, the answer should be 12.5 bcoz, when he ate 1st bowl, what was left was 92%, and after that he kept consuming 8% every time. so, here 92/8 = 11.5 ( correct ), but now we also have to add the 1st bowl which he ate. which makes (11.5 + 1) = 12.5. This is what I think. If anyone can spot any error in my judgment, please let me know.(4 votes)
- I didn't understand anything 😞(3 votes)
- After calculating the original discounted price with the 30% off

(28), an easier approach is to find a percent decrease by doing (28 - 22.20 / 28 )100. Hope that helps!(2 votes)

- where is 0.7 from?(3 votes)
- To change any decimal to a percent, you just move the decimal 2 places over to the right. With that being said, in this problem, 0.7 (or 70%) is the discounted price. How did we find out? Well the problem told us that the jeans had a 30% discount. That means you take away 30% of the original price. So you could either multiply the number (in this case $40) by 0.3 (30%) and subtract that from 40 again to get the final price of the discounted jeans, or you can do it as Sal did, which is use the rest of the percent (30% + 70% = 100%) and just multiply by 0.7 (70%) to get the discounted price without subtracting anything.(2 votes)

- how did she get the 70% it doesn't mention it on there ?(2 votes)
- 100% (Which is the original sale price)

-30% (The discount)

=70%

The 70% is the amount you pay of the original sale price. Since it's a 30% discount, then you actually pay 70%. I hope that makes sense.(0 votes)

- But if the customer recieved an additional 20% from the 30%, that would be 50% off. Therefore wouldn't the total then be $20?(1 vote)
- You've just stumbled on one of the most common misconceptions about percents. If you take the percent of a percent, this is not the same as adding the percents and then multiplying it by the given value. Instead, you would have to multiply. A 20% off of a 30% would be equal to a (0.8)(0.7) = 0.56 --> 44% discount.(2 votes)

## Video transcript

- [Instructor] We're told today, Ebuka opened a new cereal box. He ate a bowl of the cereal, which was 8% of the
cereal in the entire box. Approximately how many more
bowls of cereal can Ebuka expect to get from this box if he continues to eat
the same amount of cereal in each bowl? All right, pause this video
and see if you can answer this on your own. There are several ways that
you could approach this. You could say, all right, the box starts off with
100% of the cereal. Then in that first bowl, he eats 8%, and so you're left with 92% of the original new box amount of cereal, and then every time, he's going to eat 8%
of the original amount that was in the box. So if now we have 92% of the
original amount in the box, and at every serving, he's
going to eat 8% of it, we just divide by 8% to figure out how many servings he'd have. And so 92 divided by eight. See, eight times 11 is 88, and then you have four more, so this is going to be
11 and a half bowls, and that is this choice right over here. If the percent is confusing, you could say, all right, let's just imagine that
there were, I don't know, 100, pick a unit, in the original box. Then every serving, he eats eight, and so he's left with 92 and then if every serving,
he's eating eight, 92 divided by eight is 11.5.