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Lesson 3: Identifying proportional relationships

# Is side length & perimeter proportional?

Sal answers the question by drawing a square and thinking about the relationship between side length and perimeter.

## Want to join the conversation?

• When you think about it, it's NOT proportional bcoz what if the side lengths are different values like 3 and 7? it doesn't work then, so it wouldn't be proportional right? Or am I just overthinking?
• Then that's not a square anymore that's a rectangle, Squares have equal sides :)
• what does proportional mean??
• or this (of two quantities) having the same or a constant ratio or relation:
The quantities y and x are proportional if y/x = k, where k is the constant of proportionality.
• I understand this for a sqaure, but what If it's for a rectangle how would te sides be porportional since a rectangles has not all 4 sides that are congurent.
• If this is for a rectangle, the ratio won't be proportional any more. For rectangles can have any number from 1 to infinity for two of the sides and another number from 1 to infinity for the other two sides. If the 4 sides are the same, you get a special rectangle that you call a square.
For example, two sides of the rectangle are 4 and the other two are 6. Then the perimeter would be 4+4+6+6 which is 20, then do 20 divided one of the sides to get the proportion, for example, 20 divided 4, then you will get 5. Then get another rectangle, let's say two sides are 7 and the other two are 9. then you would have 32 for the perimeter, then 32 divided 8, and you get 4.
And now we have a proportion of 5 and another of 4. This is not a proportional relationship.
Hopefully this helps.
• Are the length and breadth of different rectangles of the same perimeter in proportion. Examine.
• math wont help us in real life-_-
• That is 100% wrong. Math is EVERYWHERE.
I'll prove it.
You have 2 other friends over and 6 slices of pizza. How many slices does each person get?
6 slices divided for 3 people is 2 slices per person.

You're at the store and want a shirt. The shirt costs \$2.00, and you have \$3.00 in total (in dollar bills). How many bills do you pay, and how many do you have left? 1+1 = 2 | 3-2=1.
You have \$1 left

You are absolutely incorrect that math won't help.
I hope this helped. I never ever want to see another comment like that again.
• it can help us in real life?
THAT IS SUCH A LIE
• You know what is a lie? You saying that math won't help is in real life, that's the lie, mpascualrodrigue8488. Please stop posting those type of comments/answer/questions. =)
• why do you repeat when you say "side length" because then i hear "siiiiiide length, side length"