10

How do read aloud the fraction 2/3 in Russian ?
Do you say:

два на три ?, два над три ? два по три ?два под три ?

or something completely different?

Edit
My example was not very good. I am actually interested in mathematical expressions like x/y: how do Russians read that aloud?

6

A fraction x/y is pronounced by mathematicians as икс на игрек. Moreover, a product xy is pronounced the same way if you want to include a word representing the operation (often you do not and would pronounce xy simply as икс игрек; a case when it is natural to pronounce the operation in a product would be x*2, unlike 2x -- in fact if you tried to pronounce x*2 as икс два then people would think you mean the indexed expression x_2). From context it would be clear if на means multiplication or division. If you think it is crazy to pronounce x/y and xy in the same way, compare with the use of the term "to scale" in English, where for instance "scaling an equation by two" could mean multiplying both sides by two or dividing both sides by two. The context makes it clear which one is meant.

If you want to be more explicit about the operation when pronouncing the notation, then x/y is икс разделить на игрек and xy is икс умножить на игрек. The way of pronouncing these expressions that I mentioned initially is just an abbreviation of these more precise terms.

19

Numerical fractions

2/3 = две третьих or две трети

The numerator of a fraction is always a cardinal number and the denominator is an ordinal number in Genitive (singular if the numerator ends in "одна" and plural if that's not the case). Always use feminine when the form exposes gender.

For quarters and thirds you can also use "одна треть" and "две четверти". Russian has words "треть" and "четверть" which mean "a third" and "a quarter" respectively. Won't work for other numbers, though—there are no such words.

Examples of other fractions:

  • 5/3 = пять третьих
  • 4/10 = четыре десятых
  • 1/8 = одна восьмая
  • 3/8 = три восьмых
  • 5/9 = пять девятых
  • 21/27 = двадцать одна двадцать седьмая
  • 49/1000 = сорок девять тысячных
  • 22/232 = двадцать две двести тридцать вторых

Note that ordinal "третий"(3rd) has a slightly deviant ending patter with "ь", typical of animal-possessive adjectives (лисий, волчий, цыплячий, кошачий). That probably has much to do with the fact that other than animal-adjectives -сий/-тий are never encountered (at least, I could not find any such adkective) and -чий is pretty rare.

Mathematical expressions

When reading mathematical expressions or if you actually mean the division of x by y with numbers (especially large), use "x поделить на y". Or just "x на y" where the context is explicit — for instance, if you are writing out the same fraction as you pronounce it, so your viewers know that you mean division and not multiplication.

For numbers (at least, small enough) you typically treat a fraction as a whole unit. When you read expressions, the latter method is the only way to go.

It may look like that:

  • 581/1035 * (x + 1.2) → пятьсот восемьдесят один ... на тысячу тридцать пять... (и) умножить на икс плюс одна целая две десятых (when spelling the expression)
  • (x²+2)/(x³ + 7x - 4) → икс квадрат плюс два (поделить) на икс куб плюс семь икс минус четыре.

Again, if you are writing a fraction for everyone to see or are just speaking to yourself, single "на" is enough. However, if a listener has no reason to assume it is division and not multiplication, it sounds ambiguous, and I would probably think of multiplication first.

6
  • По-моему можно сказать "две трети яйца", "две четверти арбуза" (например в рецепте), но в математике "две третьих интеграла" или "три целых и одна четвертая". – Artemix Sep 10 '14 at 9:34
  • Dear Shady_arc, thanks for your informative answer. Could you please look at my Edit: I am actually interested in literal mathematical expressions containing no explicit numbers (although I am happy that you explained how those are read) – Georges Elencwajg Sep 10 '14 at 9:54
  • For completeness, the reason the numerator is feminine (clear when it is 1 = одна and 2 = две) is that the number in the numerator is modifying the feminine word часть, which is not explicitly pronounced. – KCd Sep 10 '14 at 12:36
  • Awesome answer! :) – Alenanno Sep 11 '14 at 12:23
  • I see you use поделить instead of разделить, but умножить instead of помножить. Would you say these options are used equally often? I was taught to use разделить and умножить if the operation needs to be made explicit. – KCd Sep 12 '14 at 9:42
2

I would say "икс делённое на игрек" or "икс делить на игрек". If from the context it is clear that multiplication excluded, you can say just "икс на игрек" but this also can mean multiplication.

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