Breakdown of В доме пять чистых столов и десять грязных.
дом
house
и
and
стол
table / desk
в
in / to (direction)
Questions & Answers about В доме пять чистых столов и десять грязных.
Why do чистых and грязных end in -ых?
They are in the genitive plural case because they follow the numbers пять (five) and десять (ten). In Russian, numbers from 5 onwards require the following adjectives and nouns to be in the genitive plural. The dictionary forms of these adjectives are чистый and грязный, and their genitive plural ending is -ых.
Why isn't there a word for 'ones' after грязных?
In English, we say 'dirty ones' so we don't have to repeat the word 'tables'. In Russian, you don't need a placeholder word like 'ones'. You can just drop the noun and use the adjective on its own. десять грязных literally means 'ten dirty', which sounds perfectly natural in Russian.
Why is it столов instead of столы?
Just like the adjective чистых, the noun стол (table) must be in the genitive plural because it comes after the number пять. For most masculine nouns ending in a hard consonant, the genitive plural ending is -ов.
Why is it В доме and not В дом?
We use the prepositional case here (доме) because it answers the question 'Where?' to show location. If you said В дом, that would be the accusative case, which is used for motion or direction to answer 'To where?' (like walking into the house).