It is honorific to use ut as plural when it is an elder. For eg. दादाजी खाना खाते हैं, here we used खाते है, not खाता है, so we use plural for elder or to give respect, okay?
'Ka' is used for singular things, and to denote masculine nouns, 'ki' isused for feminine nouns, 'ke' is used for plural ones and also in a respectful /formal way