## Archive for October 4, 2010

### That Doesn’t Make Cents!

What’s the difference between an old penny and a new dime? Nine cents!

Why didn’t the quarter roll down the hill with the nickel? Because it had more cents.

And a math problem related to coins:

You have three coins — one is a typical coin with heads on one side and tails on the other. But the other two are strange — one has heads on both sides, and one has tails on both sides. One coin is chosen at random and placed flat on the table. It shows heads. What is the probability that the other side is tails?

Your first instinct may be to think that the probability is 1/2. But it’s not. I won’t give you the actual answer, but here’s a hint — create these “coins” using pieces of paper with H and T. Then try it several thousand times. You’ll see that if the coin shows heads when placed on the table, then the other side will not be heads and tails in equal proportions.

The Math Jokes 4 Mathy Folks blog is an online extension to the book Math Jokes 4 Mathy Folks. The blog contains jokes submitted by readers, new jokes discovered by the author, details about speaking appearances and workshops, and other random bits of information that might be interesting to the strange folks who like math jokes.

## MJ4MF (offline version)

Math Jokes 4 Mathy Folks is available from Amazon, Borders, Barnes & Noble, NCTM, Robert D. Reed Publishers, and other purveyors of exceptional literature.

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