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## 5th grade foundations (Eureka Math/EngageNY)

### Course: 5th grade foundations (Eureka Math/EngageNY) >Unit 4

Lesson 7: Topic G: Foundations

# Relating division to multiplication

Sal talks about the relationship between multiplication and division problems.

## Want to join the conversation?

• What does division have to do with multiplication?
• They are directly related to each other. Say you have 12 / 3 = 4. With this, you know that 3 x 4 = 12.
• Is this sort of the start of algebraic thinking?
( doing ( _ / 2 = 9 ) other than ( 9 * 2 = _ ) ? )
• one of the cool new things I see in this algebra stuff (which coincidentally I'm relearning right now) is that in algebra we begin to tolerate unknowns, working WITH the unknowns to arrive at the solution we're looking for. at first you usually are solving for x but gradually you learn to solve for y or z and allow x to just be x....the system still works and the rules remain the same.
eventually we come to f(x) which has a shape, identity, behavior we know (like a fractal or a sine wave) without ever having to wring any specific number out of little x
if it's all in the same system you don't always have to answer EVERY question or every portion of every question, look for what you need. work with the system to derive it
especially if your testing/contest system is using multiple choice, eliminate the wrong answers and see what's left to pick
but I digress
yes! _/2=9 and instead of "blank" you can say/write x
this is the beginning of algebra
good catch Zhang
• Okay, just putting this out there, when I'm doing math, sometimes I get confused with all of the symbols: ×,+,-,÷ etc. And I end up dong the wrong thing, like subtacting instead of adding. Does anyone have a trick they use to remember what means what? Or is it just that I have to pay more attention to the symbols when doing problems? ;P
• Both of the ones that make the number go up are a X shape and the ones smaller have a -- in them
• no idea at all...
• So say you have a home work assignment for math class, and a question asks you, "Oh, jjcdcv, fill in the blank, 49 divided by blank equals 7" So obviously you know multiplication because that's one of the the first things they taught you, so you're like "Well 7 X 7 = 49" So there's your answer 49 divided by 7 = 7.
• How can I relate division to multiplication when I'm working on Division?
• Think of it like this: When you divide 8 by 2 you are basically saying "What would I have to multiply 2 by to get 8." So instead of writing 8 / 2 = X you could write 2 * X = 8. Does this help?
• Is this the start of algebra with blanks and question marks?
• Yes, blanks and question marks are the start of algebra.
• is it reverse? than multipalcation?
• It is like reverse multiplication. Multiplication is a faster way instead of doing repeated addition, and division is a faster way instead of doing repeated subtraction.