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11/16" + 11/16"

Adding two fractions of an inch, exactly — the everyday jobsite arithmetic that a decimal calculator gets wrong. Reduced, carried, and shown in millimetres.

11/16" + 11/16" =
=1-3/8"
Sum
1-3/8"
Decimal inch
1.375"
Millimetres
34.925 mm
11/16" − 11/16"
0"
The work

Over a common denominator

Put both over 16: 11/16 = 11/16 and 11/16 = 11/16. Add the tops: 11/16 + 11/16 = 22/16, which carries past one inch. Reduced, that's 1-3/8" (1.375 inches). TapeMath tracks it as an exact fraction, so it lands dead on the tape mark.
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