Union Government
(1) Save as otherwise provided, all questions in either House (or a joint sitting) are decided by a majority of members present and voting, excluding the presiding officer, who has a casting vote only in case of a tie. (2) A House may act despite any vacancy in its membership, and proceedings remain valid even if it's later found someone not entitled to sit or vote took part. (3)-(4) Until Parliament provides otherwise, the quorum for a House meeting is one-tenth of its total membership; without quorum, the presiding officer must adjourn or suspend the meeting.
Most parliamentary decisions are made by simple majority of those present and voting, with the presiding officer voting only to break a tie. Proceedings remain legally valid even if there's a vacant seat or, oddly, even if someone not actually entitled to sit took part - and a very low quorum (just one-tenth of members) is enough to hold a valid sitting.
This is why Lok Sabha or Rajya Sabha sittings can validly continue with only a small fraction of MPs physically present in the chamber - as long as one-tenth of the total membership is present, the House can conduct business, even if many seats visibly sit empty on camera.