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## Arithmetic

### Course: Arithmetic>Unit 2

Lesson 8: Associative property of multiplication

# Using associative property to simplify multiplication

Sal uses the associative property to multiply 2-digit numbers by 1-digit numbers.

## Want to join the conversation?

• Can't we do like that 3*21 = (3*20)+(3*1)=60+3=63
For me it is much more easier to do them
like 83 *4 =(80*4)+(3*4)=320+12=332?
• Yes you can do it like that.
• There was so many numbers and number sentences I couldn't understand anything. Why are we doing so much things?
• the more you lern the better
• i dosent know how to do this very well can i has some help?
• Vote me if you want people to stop writing the video transcript
• Does this video make any sense to you?🤷‍♀️
• Yes it does.
• Does it matter, if you wrote the answer to be 15 x 3 = (3x3) x 5 = 9 x 5 = 45. / video time.
• Good question!

It doesn't. In multiplication, the product will be the same no matter what order you write the numbers:

3x4x5 = 5x3x4 = 4x5x3 = 3x5x4 = 60
• Honestly? It's sort of hard depending on how you're thinking about things. Maybe the entire concept of this flew over my head and I'm doing it the wrong way but whenever I see 14x5 my brain just multiplies 5 by whatever comes to mind that's easiest to remember.

14x5=
5x5 + 5x5 + 5x4
so
25+25+20= 70
• I say do whatever way is easier for you

For me, I'm pushing myself to relearn a bunch of old math concepts because I slept way too much in math class in grade school lol

Anyways I think what helped me build splitting up multiplication problems to do them easier was practicing the base concept of multiplication

Where 2 x 3 = 3 + 3

And Distributive Property where 2 x 3 = 2(3+3)

At first is seems pointless to do but when you practice it enough and slowly start doing bigger numbers like 6 x 9 = 6(10-1) = 60 - 6 = 54

It'll make doing math quicker not just on paper but even in your head

I just say keep practicing trying to solve math problems with different techniques and even if you got the answer in another way force yourself to solve it differently so you get the sense of different solutions
• why does the teachers make math so hard