basic triple draw probability questions

[Chris Daddy Cool]

1. suppose before the first draw i have a hand like 2357K and i want to get rid of the K, thinking a 4,6 or 8 is likely to win it for me for the duration of the draws.

a) what is the chance of me getting a 4,6, or 8 on an individual draw?

b) what is the chance of me improving by the third draw?


2. I am heads up on the last draw and draw one card and pair up for a final holding of 22357. my opponent drew one card as well and bets 4 dollars into me. basically i can only beat a bluff. how big must the pot be for me to correctly call?