There is a countless number of petals on daisies. This is simply due to the fact that there are wild variations in the amount of petals each type of daisy will have, and, even daisies of the same type will vary quite greatly.
So, in short, use a magic eight ball and be done with it.
Ummm, if you could figure it out in advance, you would then lose the prediction part of doing it randomly (if you believe in that sort of thing anyway).