The rule of likeness applies in the subtraction of fractions as well as in addition.Some examples will show that cases likely to arise may be solved by use of ideas previously developed.
Figure 4-5.-Adding fractions to obtaintotal length or spacing.
EXAMPLE: Subtract 1 1/3 from 5 2/3
We see that whole numbers are subtracted fromwhole numbers; fractions from fractions.
EXAMPLE: Subtract 1/8 from 4/5
Changing to like fractions with an LCD, we have
EXAMPLE: Subtract 11/12 from 3 2/3
Regrouping 3 8/12 we have
Practice problems. Subtract the lower number from the upper number and reduce thedifference to simplest terms:
The following problem demonstrates subtraction of fractions in a practical situation.
EXAMPLE: What is the length of the dimension marked X on the machine bolt shown infigure 4-8 (A)?
SOLUTION: Total the lengths of the knownparts.
Subtract this sum from the overall length.
The answer is 1 15/64 inch
Figure 4-6.-Finding unknown dimensionsby subtracting fractions.
Practice problem. Find the length of thedimension marked Y on the machine bolt in figure 4-6 (B).
Answer 2 3/32 inches