In normal rational arithmetic or 5 is . The result could be taken as 3 if we choose to round up.
Then of 10 is . If we round to the nearest value then we get 3. If we always round non-integers up, then we get 4.
If we simply take the antecedant " of 5 is 3"" to be false, then we can deduce any consequent, e.g. that of 10 is a herring or anything else we choose.