Complex fractions

When mixing homemade cleaning solutions, you often need to use precise ratios.

To express complex fractions (fractions with a numerator greater than one), combine a cardinal number and an ordinal number. Because you are counting "parts" (the implied masculine noun hlutar), follow these rules:

  • Numerator: A cardinal number. If it inflects (1–4), use the masculine plural form (e.g., fjórir for 4).
  • Denominator: An ordinal number in the weak plural form, which always ends in -u (e.g., fimmtu for fifths, tíundu for tenths).

When specifying a fraction of an ingredient, use the preposition af, which requires the following noun to be in the dative case.

Four fifths of the homemade glass cleaner are just water.
Fjórir fimmtu af heimatilbúna glerhreinsinum eru bara vatn.
Nine tenths of the concentrate are a natural cleaning product.
Níu tíundu af þykkninu eru náttúrulegt hreinsiefni.
The student cleans five sixths of the dirt with the cleaning product.
Nemandinn þrífur fimm sjöttu af óhreinindunum með hreinsiefninu.
We use seven eighths of the baking soda for the bathtub.
Við notum sjö áttundu af matarsódanum í baðkarið.