Your holding in H's:

K75

vs

AT9

In a 4S contract you have stripped other suits and from the bidding you know LHO has HQ and some H length (3+). LHO is on lead and plays the HQ.

Comment from the blog ('I' is LHO)

Quote

*Here there is not restricted choice on the Q, assuming I am a good defender, I know that declarer has already placed me with the Q for my bid. Accordingly, with QJ I MUST play the queen, otherwise Aaron will know that I still have it in my hand. This means it's not clear what the percentage play is in hearts. To figure it out we need to calculate the number of possible QJx(x) combinations and weigh it against the number of Qxx(x) combinations.*

**If I have 3 hearts, there are 4 QJx's possible and 6 Qxx's possible. If I have 4 hearts there are 6 QJxx's possible and 4 Qxxx's possible**!My question:

How do you calculate these odds at the table? Is there any easy logical way to do this?