This section is from the book "The American House Carpenter", by R. G. Hatfield. Also available from Amazon: The American House Carpenter.

Subtraction is the reverse of addition; therefore, to subtract fractions a reverse operation is required to that had in the process of addition; or simply to subtract instead of adding.

For example, if 2/5 be required to be subtracted from -

we have -

3/5-2/5=1/5

By reference to Fig. 274 an exemplification of this will be seen where we have A C = 3/5, A E = 2/5, and E C = 1/5, and we have -

AC-AE = EC.

3/5-2/5=1/5.

We therefore have this rule for the substraction of fractions: Subtract the less from the greater numerator; the remainder will be the numerator of the required fraction. The denominator to be the same as that of the given fractions.

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