Какой or какого question

Good morning, I have a question about when to use какой or какого.
I kinda get it why we used genitive case on number 2. but why do we not use genitive case on number 1?
I can not be " what of your size?
Please help! Thank you!

  1. какой ваш размер ?
    -десятый

  2. какого размера эти детские туфли?
    -это двадцатый размер

Hi @keepthafaith,

In sentence 1 the object is the size, that’s why it it is Nominative case: “your size is which”?
In sentence 2 the object is the shoes, so the size belong to the shoes: “the shoes of what size?”

You could say “Вы какого размера?” You of what size?, to have size in genitive, but one would never address a person in such way :slight_smile:

Hope it helps

Best of luck,

Pasha

THank you!