Dividing Fractions Part II


Dividing Fractions Part II

CA/NY.5.NF.7 

This week my daughter asked for help with the following math problem:

Melanie had 3 pounds of dried fruit. She packed the dried fruit into bags of ⅜ pound each. How many bags of dried fruit did she pack?

Having been taught math by procedure, my first thought was 'OK, well, this is a division problem, you just divide 3 by ⅜. So that's the same as multiplying 3 by 8/3.' But my second thought was 'wait a minute. That's not teaching her anything, that's just telling her what to do to get the answer.' I knew I had to approach this in a more constructivist way.

So first I drew a picture.


And then I added an equation.


And then we talked about how to turn the whole number "3" into something that would be easier to work with.


So now we had something that looked a lot more familiar to her.  


She knew that the denominator should stay the same (many thanks to her 4th grade teacher), so from there it was easy for her to see that ⅜ goes into 24/8  8 times.
OR 
3 ÷ ⅜ = 8 bags of fruit


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