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### Course: Operations and Algebraic Thinking 222-226 > Unit 1

Lesson 4: Identifying proportional relationships- Intro to proportional relationships
- Proportional relationships: movie tickets
- Proportional relationships: bananas
- Proportional relationships: spaghetti
- Identify proportional relationships
- Proportional relationships
- Proportional relationships
- Is side length & area proportional?
- Is side length & perimeter proportional?

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# Proportional relationships

Sal determines which ratios are proportionate to a ratio provided in a context.

## Want to join the conversation?

- So... Is it just me or I don't get this at all. :/(54 votes)
- I can't get this either.(16 votes)

- I still don't get how 6x0.25 is 1.5(13 votes)
- When you think about it, 0.25 is the same as 1/4, just as a different form. So if you multiply it the fraction way : 6/1 x 1/4, we get 6/4. As a decimal, 6/4 is the same as 1.5

If I'm confused about these type of questions, I use this method. So I hope you find this helpful!(31 votes)

- can we replay the video?(10 votes)
- Yes you can. Their is a replay button on the bottom left corner of the video screen.(20 votes)

**I divide***12 / 3=4*

6 / 1.5 =4

3 / .75=4(12 votes)- That is correct :)(1 vote)

- For those who don’t understand the problem, here’s a simpler explanation, hope this helps!

1. To solve the problem it is vital to understand that every time you add 15 mL of bleach to the solution you have to add 3.75 L of water.

2. We want to know how much water (L) to add when the amount of bleach (mL) we add changes, the first thing to do is to determine how much water to add per milliliter of bleach. ➡️ 15 mL (bleach) / 3.75 L (water) = 1 mL (bleach) / 0.25 L (water). Why? I divided the denominator and nominator by 15 because that way I would know how much water to put per mL of bleach.

3. Now I know that for every 1 mL of bleach Mael adds, he must add 0.25 L of water.

4. Case #1 — If we have 12mL of bleach in the solution should Mael add 3 mL of water?

1 mL bleach / 0.25 L water ➡️ multiply the nominator and denominator by 12 to find how much water should Mael add when there’s 12 mL of bleach ➡️ 1 x 12 = 12 mL bleach / 0.25 x 12 = 3 L water

Answer A is correct!(11 votes) - when you think about 0.50 is it the same as 2/4(7 votes)
- it is the same as 2/4(4 votes)

- Im tired of getting answers wrong(7 votes)
- then get them right(4 votes)

- wait i need more information to understand this(8 votes)
- These are linear equations, which has a to do with the coordinate plane, KA's
*Get Ready for Geometry*course has a unit that that could help you understand this better if you or anyone else are still wondering.(0 votes)

- the long division is confusing :((4 votes)
- Long division is the same as division and the only thing that's different is that in division there are not big numbers like long division. Also you can check it on the calculator if it's confusing. Hope that helps you understand!(5 votes)

- I watched this video twice but the 850 energy points were never added to my score. I also completed several exercises and those energy points never were added. Why isnt this working and how do I get it to work?(4 votes)
- Hello, uhohspaggetio6.

Possibly you skipped through or maybe set the speed too high.

Maybe you skipped a bit? It could have been added but you didn't notice the change? Maybe try rewatching at a normal speed (if it wasn't normal already)

If that still doesn't work, contact the Khan Academy Help Desk at https://support.khanacademy.org/hc/en-us.

Hope this helped!(3 votes)

## Video transcript

- [Instructor] We're told
that Mael mixes 15 milliliters of bleach with 3.75 liters of water to make a sanitizing
solution for a daycare. The amounts of bleach and water always have to be proportional when he makes the sanitizing solution. Which of the following could
be combinations of volumes of bleach and water for
Mael's sanitizing solution? And they gave us,
actually they gave us five potential combinations,
they say pick three. So I encourage you to pause this video and try to figure it out. Remember, he mixes 15
milliliters of bleach for every 3.75 liters of water. Alright, now let's try
to work this together. So I'm gonna make a table here. So let's say this is bleach,
bleach in milliliters. And lets say this is water in liters. And they tell us that
he mixes 15 milliliters, the unit here is milliliters, for every 15 milliliters of bleach for every 3.75 liters of water. So what is the
proportionality constant here? If you said the water is
equal to some constant times the bleach, well what's going on? Well let's see, what would
he have to multiply by? He would have to multiply by 3.75 over 15. Now what is 3.75 divided by 15? Let me actually do it right over here, 15 goes into 3.75. Let's see, 15 goes into 37 two times, we have our little
decimal right over here, two times 15 is 30, subtract seven, bring down the five and
then 15 times five is 75, five times 15 is 75, it all works out. So we see to go from bleach to water we're multiplying by a
proportionality constant of 0.25. So we have to see which of these have the same exact
proportionality constant going from bleach to water. So let's see, this next
one is 12 and three. So if we multiply 12 by 0.25, do we get three? Yeah, three is one fourth
of 12, 0.25, 25 hundredths is the same thing as one
fourth so this one checks out. What about going from six to 1.5? Are we multiplying by 0.25? Yeah, 1.5 is one fourth of six or another way to think about it is what is six times 25? It is a 150 so six times 25 hundredths would be a 150 hundredths
which is the same thing as 1.5. So this one works. What about three and 0.75? So three and 0.75. Am I multiplying by 0.25? Yeah, if I multiply three
times 25 hundredths, I get 75 hundredths so that works. So actually the first three
choices are our three answers but let's just verify that the next two are not good answers. So let's see, if I go from 20 to 5.5, and so am I multiplying by 0.25? No, 0.25 which is the
same thing as one fourth, one fourth times 20 is five, not 5.5. So that doesn't work. And then going from 11 to 3.75, well we definitely know
that's not gonna work because notice we have
the same amount of water but we have less bleach. Or you could say what's one fourth of 11? Well that's going to be less than 3.75 so we can rule both of these choices out.