[Cobra]

Here is another way at looking at the problem.

Case one you get a 4 or 8 on the turn, there is 8 outs and 47 cards. = 8/47 = 17.02%

Case two you get a 3 or 9 on the turn, there is 8 outs and 47 cards. = 8/47 = 17.02%

Now in case one you now have an open ended straight you can get a straight by hitting either a 3 or 9, so the chances of getting a straight are 8/46 = 17.39%

Now in case two you have a gut shot straight draw, you can get a straight by hitting only one specific card, the chances of getting a straight are 4/46 = 8.7%

With this information we will find the chance of getting a straight is

= 17.02% * 17.39% + 17.02% * 8.7% = 4.44% same answer as the combination technique.

Cobra