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Question from Kathy, a parent:

1 3/4 + 1 2/3= ?

5 1/2 - 2 5/6= ?

Hi Kathy,

I'm going to illustrate the procedure by doing a similar question

\[3 \frac25 + 2 \frac38.\]

First of all $3 = \large \frac{3 \times 5}{5} = \frac{15}{5}.$ Similarly $2 = \large \frac{16}{8}$ and hence

\[3 \frac25 + 2 \frac38\ = \frac{15}{5} + \frac25 + \frac{16}{8} + \frac38\ = \frac{17}{5} + \frac{19}{8}.\]

To add $\large \frac{17}{5}$ and $\large \frac{19}{8}$ I ned the two fractions to have a common denominator. I can find a common denominator by multiplying the two denominators and hence $5 \times 8 = 40$ is a common denominator. Thus

\[ \frac{17}{5} + \frac{19}{8} = \frac{17 \times 8}{5 \times 8} + \frac{19 \times 5}{8 \times 5} = \frac{136}{40} + \frac{95}{40} = \frac{231}{40}. \]

Now try your problems,
Penny

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