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3/8" + 7/8"

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

3/8" + 7/8" =

=1-1/4"

Sum

1-1/4"

Decimal inch

1.25"

Millimetres

31.75 mm

3/8" − 7/8"

-0-1/2"

The work

Over a common denominator

Put both over 8: 3/8 = 3/8 and 7/8 = 7/8. Add the tops: 3/8 + 7/8 = 10/8, which carries past one inch. Reduced, that's 1-1/4" (1.25 inches). TapeMath tracks it as an exact fraction, so it lands dead on the tape mark.

Keep going

3/8" to decimal 7/8" to decimal All fraction sums Add it on the calculator

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