def coerce(num_units, den_units)
      Number.new(if unitless?
                   value
                 else
                   value * coercion_factor(@numerator_units, num_units) /
                     coercion_factor(@denominator_units, den_units)
                 end, num_units, den_units)
    end
def coerce(num_units, den_units)
      Number.new(if unitless?
                   value
                 else
                   value * coercion_factor(@numerator_units, num_units) /
                     coercion_factor(@denominator_units, den_units)
                 end, num_units, den_units)
    end
Returns this number converted to other units.
 The conversion takes into account the relationship between e.g. mm and cm,
 as well as between e.g. in and cm.

 If this number has no units, it will simply return itself
 with the given units.

 An incompatible coercion, e.g. between px and cm, will raise an error.

 @param num_units [Array<String>] The numerator units to coerce this number into.
   See {\#numerator\_units}
 @param den_units [Array<String>] The denominator units to coerce this number into.
   See {\#denominator\_units}
 @return [Number] The number with the new units
 @raise [Sass::UnitConversionError] if the given units are incompatible with the number's
   current units