Tuesday, January 26, 2010

Converting fractional units into mixed units

We now present two different methods for unwrapping a fractional part into mixed units.

Suppose now that we wish to convert `5\frac{7}{9}` yards into yard, feet, and inches.

In the first method, we proceed by splitting into whole and fractional parts, and rewriting the fractional part in smaller units, e.g

`\qquad\qquad\qquad 5" yards"  +  7/9" yards"  =  5" yards"  +  7/3" feet",`
`\qquad\qquad\qquad\qquad =  5" yards"  +  2 1/3" feet,"`
`\qquad\qquad\qquad\qquad =  5" yards"  +  2" feet"  +  1/3" feet,"`
`\qquad\qquad\qquad\qquad =  5" yards"  +  2" feet"  +  4" inches."`

In the second method, we first multiply `5\frac{7}{9}`,  by `3` and by `12`, to get `208`, and then we use successive division as in the last posting.  We can even shorten this method by extracting the `5` first, multiplying just the `\frac{7}{9}` by `3` and by `12` to get `28`, and then dividing as before; this spares us the last division : `28  =  2_{12}4.`

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