O: orange juice concentrate in the first container / W: water in the first container / O′: orange juice concentrate in the second container / W′: water in the second container / The most natural ratios to be considered are O/W and O′/W′, O/O′ or O′/O and W/W′ or W′/W, O/B and O′/B′, W/B′ and W′/B′. Because differences rather than quotients also can be used under certain conditions, there are many ways of arriving at the right decision about the relative “orangeyness” of beverages B and B′.
Source: wiktionary