Tuesday, February 02, 2010

How Did You Know There Were Fifty Coins?

Mary had a coin purse with fifty coins, totaling exactly \$1.00.  Unfortunately, while counting her change, she dropped one coin.  What is the probability that it was a penny?

1. 40 pennies
8 nickels
2 dimes
80 % probability that the dropped coin is a penny

Donnie scharm@ureach.com

2. hmmmm.... I got 90%, because of 45 pennies, 1 quarter, 2 nickels and 2 dimes.

3. Which means, between the two of you, you figured out the two different ways you can get \$1 out of 50 coins.

Since we have no indication of which of the two Mary had, the chances are even it was either. That means the probability of the coin being a penny is 85%.

Leave your answer or, if you want to post a question of your own, send me an e-mail. Look in the about section to find my e-mail address. If it's new, I'll post it soon.

Please don't leave spam or 'Awesome blog, come visit mine' messages. I'll delete them soon after.

Enter your Email and join hundreds of others who get their Question of the Day sent right to their mailbox