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Topic review (newest first)

MargaritaMc
2013-02-14 00:03:07

Thank you again, Bob. Yes, the ideas are easier than the names!
I was doing the exercises at the mathopolis link where they ask you to click on which law was in operation for a given equation. I knew what the equations were doing but I kept getting the name wrong!

Margarita

bob bundy
2013-02-13 23:23:18

hi Margarita,

Haven't got a 'mnemonic'  as such but this is what I do:

Commutativity:

A x B = B x A etc

At rush hour  people from town A get in their cars and drive to work in town B. And people in town B get in their cars and drive to work in town A.  At the end of the day, they all swap back.  I believe that's why they are called commuters; because they swap over.

Associativity:

If you've got three numbers to multiply / add / divide etc, which ones do you associate together first?

A # B # C ? 

Is it A # B, get the answer and then do (answer # C)

Or is it B # C, get the answer and then do (A # answer).

So it's all to do with the ones you associate together first.

# is an associative operation if

(A # B) # C = A # (B # C)

Distributivy:

A # (B @ C) where # and @ are different operations you can do with 2 numbers.

So A has to be distributed to the contents of the bracket; B gets it and C gets it:

(A # B) @ ( A # C)

You are probably learning which operations are commutative, associative and distributive over another operation.

What is correct in each case is much more important than remembering the correct word, so I shouldn't worry too much about them.

Hope that helps,

Bob

MargaritaMc
2013-02-13 21:45:20

I find myself getting stuck on the NAMES 'commutative', 'distributative' and 'associative' - they are introduced in the Kindergarten level at the website...

Has anyone got a mnemonic for remembering them?
Margarita

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