The poker odds chart below shows the probabilities of obtaining various winning hands in Texas Odds /probability of flopping a backdoor flush draw, 1.4 to 1 Odds /probability of hitting an open-ended straight draw on the river card, 4.8 to 1.
1). the only way you could possibly make a straight flush is if your hand becomes: There are five board cards in hold'em. Since you start with.
The worst case for a possible straight flush is holding something like A2s Since 40 of those are straight flushes, the odds of flopping a straight.