Arithmetic Grade Five

Lesson One Hundred and Four: Cross Reducing

It's important to realize that cross-reducing is a useful short cut and that it gets you the same answer as you would get if you multiplied and then reduced. 


	1	  3	   3      1
       ---   *   ---   =  ---  = ---
	3         5        15     5
If we cancel out the threes first, we don't have to reduce after multiplying. 

	1	  3	   1
       ---   *   ---   =  --- 
	3         5        5
Here's one more example: 

	1	  6	   1
       ---   *   ---   =  --- 
	6         9        9

If we reduced after multiplying we'd have something that looks more like
this:

	1	  6	   6       1
       ---   *   ---   =  ---  =  --- 
	6         9        54      9

Now you get to try a few for yourself.

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