code: public static int getInheritedScale(AbstractCalculator calc, Num value) {
          if (value.getScale() == null) {
              if (calc != null && calc.getScale() != null)
                  return calc.getScale();
              else
                  return Properties.DEFAULT_SCALE;
          }
          else
              return value.getScale();
      }
docs: If {@link Num} don't define scale then use scale from {@link AbstractCalculator} instance.
  Othervise use default scale {@link Properties#DEFAULT_SCALE}
  
  @param calc
  @param value