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1/8" + 3/8"

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

1/8" + 3/8" =

=0-1/2"

Sum

0-1/2"

Decimal inch

0.5"

Millimetres

12.7 mm

1/8" − 3/8"

-0-1/4"

The work

Over a common denominator

Put both over 8: 1/8 = 1/8 and 3/8 = 3/8. Add the tops: 1/8 + 3/8 = 4/8. Reduced, that's 0-1/2" (0.5 inches). TapeMath tracks it as an exact fraction, so it lands dead on the tape mark.

Keep going

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