Tuesday, May 17, 2011

"Ask Dr. Steve"

Ask Steve Sharpe a mathematical stumper! Dr. Sharpe holds a PhD in Mathematics from Stanford University.

Q: A box contains two coins. One coin has heads on both sides. The other coin has heads on one side and tails on the other. A coin is selected at random, and the face of one side is observed. If the face is heads, what is the probability that the other side is heads?
-Rich Vinino, New Jersey

A: Let’s label the double-headed coin “Head 1” and “Head 2,” for each side. Then the regular coin we’ll call “Head” and “Tails.” So we have an equal chance of seeing any of these faces: 1 in 4 for each. Then in the puzzle, you see one of the heads which eliminates…Hey, what’s going on over there? Stop that! Put that down! That’s my TV! Oh come on. I can’t believe this. I just bought that TV! I guess I was so focused on these coins I didn't hear him come in. He left a note. Wait a second…Thanks for the TV and Good Luck with the Math Problem, Love, Rich Vinino? You’ve got to be kidding me. This is what I get for helping you idiots understand basic math? Well, for your information the answer is two out of three and also you cut your arm on my window and I’m going to sequence your DNA and find you and there’s also a 66% chance I steal your identity, Rich Vinino, because I can easily do that.

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