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## 7th grade (Eureka Math/EngageNY)

### Course: 7th grade (Eureka Math/EngageNY) > Unit 1

Lesson 4: Topic D: Ratios of scale drawings- Exploring scale copies
- Explore scale copies
- Corresponding points and sides of scaled shapes
- Corresponding sides and points
- Identifying scale copies
- Identify scale copies
- Identifying scale factors
- Identify scale factor in scale drawings
- Identifying values in scale copies
- Scale drawing: centimeters to kilometers
- Making a scale drawing
- Construct scale drawings
- Interpreting a scale drawing
- Solving a scale drawing word problem
- Scale drawing word problems

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# Scale drawing: centimeters to kilometers

CCSS.Math:

Sal uses ratios to figure out how far apart two cities should be on a map. Created by Sal Khan.

## Want to join the conversation?

- so... basically you just do x6 to both? .(106 votes)
- yes its like equivalent fractions.you know when you multiply the numerator and the denominater by the same number.(4 votes)

- I did the "ratio word problems" by the way at below :

for example :

Laine reads 25 pages in 30 minutes.

If Laine reads 200 pages in a same rate, how long will it take her?

I did like this: 25=30

200=?

I used 200*30 then divide 25 and the answer is 240 which is an correct answer.

Can I find any answers from this type of question by the solution above?

Thank you.(4 votes)- Yes, this is a correct way to solve ratio problems. (25:30and 200:? would be the correct way to write it. 25 does not equal 30.)(1 vote)

- I got this question and I'm not sure how to solve it

A 17 Oz box of Special K for $4.89 or a 21 Oz box of Cheerios for $5.69. Which is the better deal?

Thanks(0 votes)- Your problem is a typical problem involving unit prices. The better deal is the one with the lowest unit price. You can calculate any unit price by doing: Price ÷ Units (in this case ounces). So, here are the steps you need to do.

1) Calculate the unit price for the Special K: 4.89 ÷ 17

2) Calculate the unit price for the Cheerios: 5.69 ÷ 21

3) Compare your 2 answers. The one with the lower unit price is the better buy.

Here's a video on unit prices: https://www.khanacademy.org/math/pre-algebra/pre-algebra-ratios-rates/pre-algebra-rates/v/finding-unit-prices

Hope this helps.(8 votes)

- this is hard😰😡(3 votes)
- Im still really confused(2 votes)
- mr.khan i have a question>The ratio between the length sides of a triangle is 2:3:4.Ig the perimeter of the triangle is 54cm,find the length of each side of triangle(2 votes)
- Answer: 2:3:4 equates to12:18:24 = 54cm(1 vote)

- how do you do that I don't get it at all(2 votes)
- can you use the criss-cross method on this(2 votes)
- How do you solve a ratio comparing 3 quantities?(1 vote)
- First you find out how much time would take to let 5 people to paint 5 wall. Then you find out how long do it take to let 6 person to paint 1 wall. The answer should be 6.6repeat, round to 6.67.(2 votes)

- Ok, can someone please explain the different between this video and the one before=?

In the first video, with students, the girl to boy ratio is 5 to 8 ( 5:8, 5/8). Let's say 5 is g and 8 is b and totalt is t. Then we get: Ratio g:b = 5:8 --> g+b=t 5+8=13

But in this video example we can't do that. 7cm : 10km can't be written as a:b = 7 : 10 and a+b=t --> 7 + 10^6=total.

What is the different between the ratio problem of girls and boys and this problem of scale?(0 votes)- Exactly. You can't put it in that equation, due to the fact that you have two different measurements. You would need to divide 65 by 13, find how many times one part goes into the whole. At the end you will have a total result. Therefore, your equation is incorrect.(1 vote)

## Video transcript

The scale on a map is 7
centimeters for every 10 kilometers, or 7 centimeters
for 10 kilometers. If the distance
between two cities is 60 kilometers-- so
that's the actual distance-- how far apart in centimeters
are the two cities on the map? Well, they give us the scale. For every 10 kilometers
in the real world, the map is going to
show 7 centimeters. Or another way to
think about it is if you see 7 centimeters
on the map, that represents 10 kilometers in the real world. Now, they're saying that the
distance between two cities is 60 kilometers. So it's essentially 6 times
10 kilometers, so times 6. So if you have to 6 times
10 kilometers on the map, you're going to have 6 times
7 centimeters, so times 6. And 6 times 7 centimeters
gets you to 42 centimeters. So how far apart in centimeters
are the two cities on the map? Well, 42 centimeters.