fractions are formed as: (how much parts), expressed by cardinal number in case of the phrase, plus (of how numerous parts), expressed by ordinal number; the construction is formed as like it were related to word "part" (grammatically feminine), which is usually omitted. noun to such construction always comes in genitive single, also as like it belonged to word часть: "92/50 tons". if an integer precedes a fraction, it is bound to it usually with the conjunction , while the noun remains in genitive: "2 3/8 turns" ( is masculine, so the numeral is , not *).