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| Math Central | Quandaries & Queries |
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Question from lenora, a student: explain an error pattern in each of the following. 8 3/8 - 6 1/4 = 2 2/4 |
Hi Lenora,
Let me try a different problem, $5 \frac23 - 2 \frac49.$ The integer part is, $5 - 2 = 3.$ When you subtract the fractions however you need a common denominator. $\frac23 = \frac{2 \times 3}{3 \times 3} = \frac69$ and hence
\[\frac23 -\frac49 = \frac69 - \frac49 = \frac{6 - 4}{9} = \frac29\]
and thus
\[5 \frac23 - 2 \frac49 = 3 \frac29 \]
Now try tour question,
Penny
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