Quote Originally Posted by hills View Post
Not quite sure about the statistics and odds of them being all heads up in a penny roll. How on earth would one ever calculate that ? The problem is that there's a 50/50 chance that the coin will land heads up when you randomly drop the first coin in. It's the same chance when you drop the second coin in.



The problem is that they're two separate events so you can't add or multiply the odds.
It is actually quite simple to calculate the odds. The odds of two coins facing the same direction is 1 in 2. You can have heads/heads or tails/tails. You could also have heads/tails or tails/heads.

3 coins- 1 in 4
4 coins- 1 in 8
5 coins- 1 in 16

You keep doubling the number and it will get to be a pretty staggering number in a short while.

This is like the old story where someone says that if you give someone a penny and double it each day for 30 days that you will have over a million dollars in a month.

The tricky part about this exercise is in considering extraneous items that might skew the results. Someone in this thread mentioned dealing with someone with obsessive/compulsive disorder, for instance.