My girlfriend and I were having a debate about a magic trick that could be used to pick up women on the street.
I am a magician and I have a coin. I walk up to a complete stranger with the coin in my hand and know which side is up. I ask her to state heads or tails. If she picks the correct one I tell her, "I knew you would pick that one. You should marry me!". If however, she doesn't pick the one I know that I have in my hand facing up. I flip the coin, and if I get it correct, I instead say, "You should go and get it drink with me immediately!"
What there chances that she will be told either that she should marry me or go out and get a drink with me? I have a 50% chance of her getting the first line 100% of the time. That leaves another 50% unaccounted for. I now have a 50% chance of her getting the second line, but only 25% of a chance over all.
Can these two numbers be added together to get 75% chance total? My girlfriend says it doesn't work like that I am wrong.