Welcome to BrainDen.com - Brain Teasers Forum
|Welcome to BrainDen.com - Brain Teasers Forum. Like most online communities you must register to post in our community, but don't worry this is a simple free process. To be a part of BrainDen Forums you may create a new account or sign in if you already have an account.
As a member you could start new topics, reply to others, subscribe to topics/forums to get automatic updates, get your own profile and make new friends.
Of course, you can also enjoy our collection of amazing optical illusions and cool math games.
If you like our site, you may support us by simply clicking Google "+1" or Facebook "Like" buttons at the top.
If you have a website, we would appreciate a little link to BrainDen.
Thanks and enjoy the Den :-)
Posted 14 December 2007 - 07:40 PM
Answer: One easy solution is to consider all 50 pennies to be in one pile, then randomly select 30 pennies for a second pile, turning all those pennies over. Since you started with exactly 30 heads, you are guaranteed to have the same number of heads showing in each pile.
Why does this work?
Consider that you randomly select N heads out of the original 30, leaving 30-N heads in the first pile. Since you selected 30 coins, N of which are heads, this means that you also have selected 30-N tails into the second pile.
Huh. Look at that. You have 30-N heads in the original pile and 30-N tails in the new pile. If only there were some way to reverse the heads and tails in the new pile...
Posted 14 December 2007 - 10:35 PM
the same number of pennies HEADS UP in each pile not the same number of pennies total.
Ah! I think this is where it was unclear. So it's perfectly valid to have one pile of one penny and one pile of 49 pennies, correct?
The way you presented it it seemed you wanted equal numbers in the piles. I see where you are going with this now. Nice one.
Posted 18 February 2008 - 03:32 PM
So here it goes:
0 user(s) are reading this topic
0 members, 0 guests, 0 anonymous users