Our QRH specifically states that speed increments are additive but distance factors are cumulative, i.e. you multiply by 1.3 for the extra speed/less drag of failed flaps
then by 1.4 for the lack of anti-skid
However, since the starting figure is the actual landing distance, not the field length required for normal landing (ALD x 1.67) it's not as bad as it first looks. Your example gives a total factor of 1.82, so not dramatically longer than your normal runway.
