Odds of Floping a Straight Draw

[farf]

Hi all. Somehow I found myself in a bit of an argument with a friend over the odds. We are trying to figure out what the chances of floping a straight draw with connected cards, and what the mathematics are behind it. I have an answer but I cannot seem to find anywhere to substansiate it. I was hoping someone here could help me.

More specifically, if you have a 9-T, what is the chance you will flop a straight draw.

The answer I came up with is 10.51972789%

Looking forward to hearing your answers.

Farf