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### Course: MAP Recommended Practice>Unit 8

Lesson 9: Scale drawings

# Scale drawing: centimeters to kilometers

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? .
• yes its like equivalent fractions.you know when you multiply the numerator and the denominater by the same number.
• i hate math my teacher is forcing me to sit down and watch it for like 10 hours every quarter and tortores me with random assignments that spend hours on guessing until i get it
• i guess, it will help in your future exams........maybe.
• So basically the number you multiply by depends on the ratio between the scale factor and the other number?
• Yes, it is.
• 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
• 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

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.
• 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.
• Yes, this is a correct way to solve ratio problems. ( and 200:? would be the correct way to write it. 25 does not equal 30.)
• I have no idea what this man just said
• maybe re-watch it again.
• Im still really confused