[A_C_Slater]

Here's another way to get exact percentages using the Ghetto method. Take the flush draw on the flop 4x9= 36%

For every number of outs over 8 take that number and subtract it from the number of total outs 9-8= 1 36%-1 = 35% and you get the exact number.

Here it is for 15 outs. 15 x 4= 60%

15-8 = 7 60% -7 = 53%

Your 15 outs are 53% favorite.