Friday, January 23, 2015

Change a Mixed Number into an Improper Fraction

Here is a math hack I learned a few years ago from Danica McKellar's book Math Doesn't Suck:

In the textbook my school uses, improper fractions and mixed numbers are covered in one lesson. Students are expected to be able to change a mixed number into an improper fraction, and an improper fraction into a mixed number. These are separate skills. You use different processes. I like to start with changing a mixed number into an improper fraction. Here is how I teach it...

I start with MAdd Face.
MAdd stands for Multiply then Add. The x and the + are eyes. See the frown?

Here is this lesson's banner problem (a.k.a. the example problem).

First, I write the mixed number. Second, I draw MAdd Face sideways, in between the whole number (2) and the fraction (1/4).
Next, I'll multiply 4 x 2 (multiply the denominator by the whole number). That gives me 8. I'll take that 8 and add 1 (the numerator). That gives me 9, my new numerator. The denominator stays the same (4). Finally, I have my answer: 9/4.

Here it is again, with pictures...

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