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## 7th grade (Eureka Math/EngageNY)

### Unit 1: Lesson 2

Topic B: Unit rate and constant of proportionality- Intro to rates
- Unit rates
- Solving unit rate problem
- Solving unit price problem
- Constant of proportionality from equation
- Constant of proportionality from equations
- Identifying constant of proportionality graphically
- Constant of proportionality from graphs
- Constant of proportionality from table (with equations)
- Constant of proportionality from tables (with equations)
- Comparing proportionality constants
- Compare constants of proportionality
- Interpret proportionality constants
- Interpret constants of proportionality
- Worked example: Solving proportions
- Solving proportions
- Writing proportions example
- Writing proportions
- Proportion word problem: cookies
- Proportion word problem: hot dogs
- Proportion word problems
- Equations for proportional relationships
- Writing proportional equations from tables
- Writing proportional equations
- Interpreting graphs of proportional relationships
- Identify proportional relationships from graphs
- Interpreting graphs of proportional relationships
- Interpret constant of proportionality in graphs

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# Solving unit rate problem

CCSS.Math:

Jayda takes 3 hours to deliver newspapers on her route. What is the rate per hour at which she delivers the newspapers? Created by Sal Khan and Monterey Institute for Technology and Education.

## Want to join the conversation?

- Does anyone understand why Sal had to flip the 3/189 to 189/3 before he did the problem?(290 votes)
- Fractions is basically dividing.

For example 189/3 (improper fraction) = 189/3 <- Divide symbol "/" It's like simplifying it, 189/3 and 3/3 = 63/1. If he flipped it around to 3/189, then it would become smaller (3 hours for every 189 newspapers, or 3 divided by 189), simplified as 1 hour for every 63 newspapers (1 divided by 63), but it would be as decimal form if you divide it (1 divided by 63 and 3 divided by 189, both equals 0.0158730158730159, etc.) = 0.0158730158730159...(irrational number, random numbers forever going on, like pi). But if it was 189/3 (we are dealing with whole numbers) we can turn it into a mixed number: 3 can go in 189 "63" times perfectly, so 63 0/189. So that's how we got our answer. (Or 189 divided by 3, but the other way around. See how 189 divided by 3 (189/3) is different that 3 divided by 189? (3/189) ) Order matters.

I hope that made sense and helped you!(67 votes)

- Is 2:5 the same as 5:2(57 votes)
- The order of the #s matter.

If the problem were (for example) There are 15 kids who have pets in a class. There are 33 kids in the class. What is the ratio of kids who have pets to kids who do not? The answer would be15:18. If you said18:15you would be saying the ratio of kids who do**NOT**have pets to kids who**DO**have pets.(21 votes)

- Yes tis has helped me a lot now I will die as a happy man(10 votes)
- wow that doesn't sound good ur not old yet(1 vote)

- how do i solve a unit rate problem if there are fractions in them? For example, the unit rate of 2/3 cup of sugar for every 1/2 teaspoon of vanilla(6 votes)
- Divide 2/3 and 1/2. Do the same method even if it's a fraction.(4 votes)

- I don't understand these problems...

Fill in the blank with the unit rate:

240 km in 2.5 hours =*____*km in 1 hour

Fill in the blank with the unit rate:

$15 for 4 quarts = $ for 1 quart

There are 25 computers in a math lab. There are 6 activity booklets for every 2 computers in the math lab. How many activity booklets are in the math lab?

There are activity booklets in the math lab.

You earn $102 for doing 12 hours of yard work. Your friend earns $120 working at a store for 15 hours.

How much do you earn for every hour of yard work? $ per hour

How much does your friend earn each hour at the store? $ per hour

What would YOU earn for 15 hours worth of yard work (at your hourly rate)? $ for 15 hours of work(8 votes)- what helps me is writing the numbers out in a fraction. the first one, how many kms are in one hour if 240 are in 2.5, or 2 and a half, or 2 hrs and thirty minutes. you divide both 2.5 and 240 by 2.5 to get the original ratio.(0 votes)

- the ratios are the same with 5 apples and 6 banana too so it is it is still 5.6 or 6.5(7 votes)
- what is unite rate though?(4 votes)
- Unit rates are used to find out how much things happen at a time or ex. rooms per hotel.(7 votes)

- What is the difference between unit rates and price?(2 votes)
- unit rates always have a denominator of one. When prices are expressed as a quantity of one, they are called unit prices. A price is how much you actually pay. The unit price is just per one thing. :)(9 votes)

- What if the numerator is not divisible by the denominator? For example, 42 cupcakes can be made every 30 minutes. How many cupcakes can be made in 1 minute?(3 votes)
- It depends on the question.

Example:

7 leaves fall from the tree every 3 minutes. ABOUT how many leaves will fall from the tree in 1 minute?

Answer:

You would divide 7 by 3, which equals 2.3333333.... Since the question asks ABOUT how many, you can round it to 2. since 2 times 1 equals 2,then that is your approximate answer.

Hope this helps!(6 votes)

- You basically divide both by a divisor then simplify.

-Tell if it helps.(5 votes)

## Video transcript

Jayda takes 3 hours to deliver
189 newspapers on her paper route. What is the rate per
hour at which she delivers the newspaper? So this first sentence tells us
that she delivers, or she takes, 3 hours to deliver
189 newspapers. So you have 3 hours for
every 189 newspapers. That's what the first
sentence told us. But we want to figure out the
rate per hour, or the newspapers per hour, so we can
really just flip this rate right here. So if we were to just flip it,
we would have 189 newspapers for every 3 hours, which is
really the same information. We're just flipping what's in
the numerator and what's in the denominator. Now we want to write it in as
simple as possible form, and let's see if this top number
is divisible by 3. 1 plus 8 is 9, plus 9 is 18. So that is divisible by 3. So let's divide this numerator
and this denominator by 3 to simplify things. So if you divide 189 by 3. Let's do it over on the
side right here. 3 goes into 189. 3 goes and 18 six times. 6 times 3 is 18. Subtract. Bring down the 9. 18 minus 18 was nothing. 3 goes into 9 exactly
three times. 3 times 3 is 9, no remainder. So if you divide 189 by 3, you
get 63, and if you divide 3 by 3, you're going to get 1. You have to divide both the
numerator and the denominator by the same number. So now we have 63 newspapers
for every 1 hour. Or we could write this as 63
over 1 newspapers per hour. Or we could write this as 63,
because 63 over 1 is the same thing as 63 newspapers
per hour.