Mixed Fraction Subtraction - Let's Go Shopping

Mixed Fraction Subtraction - kinda rolls off the tongue, doesn't it?

OK - how about...?


     4
5  ---
     7

subtract

     5
4  ---
     7


We know the 4 and 5/7 is smaller than the 5 and 4/7.

But how to subtract 5/7 from 4/7?

Some might suggest converting both fractions to improper fractions...

...and coming up with 39/7 - 33/7 

...and arriving at 6/7.

However, if you are not particularly strong at multiplication, you might try this method...

Let's go shopping...

     4
5  ---
     7

First off - let's just make the 5 one LESS.

Why?

1) Because we can.
2) You always come away with LESS money when you go shopping. (Yes, yes, yadda, yadda, you might end up shopping for lottery tickets and win. Heard that one. Heard 'em all.)

So now our fraction is modified a bit from

     4
5  ---
     7


To...

     4
4  ---
     7


But not for long. Now let's buy a top.

Hmm, stylish. Who said I had no taste?






OK. Now remember...our top (denominator) was 4.

Better now add some pants to this stylish ensemble.

Let's add the
bottom (pants) to the
top. Can this ensemble get any more stylish? I doubt it. 


4  add  7 = 11










Remember...
     4
5  ---
     7


changed to...

     4
4  ---
     7

and we are now going to add the pants (bottom) onto the top

4  add  7 = 11


    11
4  ---
     7

Now we can finish the question.

    11
4  ---
     7

subtract

     5
4  ---
     7


Let's get rid of those whole numbers...
4 - 4 = 0

Now...

11/7 - 5/7 = 6/7


6/7 is our answer. Work SMART, not HARD!