The odds of a birdie (one shot below par) are estimated by some bookmakers to be a million to 1, or 0.000001. We'll call the probability b. That means the chances of not scoring a birdie are 1-b. So in an 18-hole course there is a chance of b for each hole of scoring a birdie. The chances of scoring all birdies is b^18. The chances of scoring a birdie on any hole in 3 consecutive rounds is b^3 and the chances of it being the same hole is b^3/18. Taking b to be 0.000001 or 10^-6, this probability becomes (10^-18)/18. For a skilled golfer b may be considerably smaller, let's say 1 in 1000, or 0.001, so b^3/18=(10^-9)/18=5.56*10^-11. There's an alternative answer, because we haven't considered the scoring on the other holes. If there was only one hole where a birdie was scored, we have to consider the chances of failing to score a birdie at the other 17 holes, which is (1-b)^17=0.999997 for b=10*-6 and 0.9970 for b=0.001. b-1 includes scores better than a birdie (like aces) as well as worse scores. So the full answer is 18b^3(1-b)^51 because there are 18 holes and we are selecting just one out of the 18 for each round. At least I think that's the answer!