gutshot by flop, double gutshot by turn

[ccwhoelse?]

what are the chances of making a straight by the river if you flop a gutshot, and can improve to a double gutshot on the turn.

for example, if you have 9Ts and the flop is 8 2 Q
you would have four Jack's to make your Queen high straight by the river. you would also have 8 outs for any 6 or 7 that gave you another gutshot straight draw to a 10 high straight.

what is the chance, by the river that you either
improve to a double gutshot on the turn and then make either straight on the river
or you make only your original gutshot.

can you do the following?


hitting a Jack by the river: 16.5%

getting a 6 and then 7, or 7 and then 6 on the turn then river: 1.5%

so it's approx around 18% which is like a 4.5 to 1 shot.
this situation is obviously better then only an inside straight draw. is the 4.5 to 1, 18% figure correct or just an approximation at best? if it is not exact, what would be the exact probability?

would you need better pot odds because you might have to call a bet on the turn to see the river?

is this a scenario worth looking for when you flopped an inside straight draw?

[Copernicus]

very good estimate (or exact and rounded) 4.57/1 to improve 9t 82Q to a straight