All about flooble | fun stuff | Get a free chatterbox | Free JavaScript | Avatars
 perplexus dot info

 Flipping Coins (Posted on 2004-10-13)
You play a coin flipping game with 5 coins. On round 1 you flip all of them. On round 2, you pick up all the ones that came up tails (leaving all the heads alone) and flip them again. You continue to do this until all the coins are heads. For example:
```Round 1:  H T T H T
Round 2:  - H T - H
Round 3:  - - T - -
Round 4:  - - T - -
Round 5:  - - H - -
```
Done in 5 Rounds.

What is the expected number of rounds you'll need to finish the game?
What is the probability you will finish the game in 3 rounds or less?

 See The Solution Submitted by Brian Smith Rating: 3.7143 (7 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
 re(2): New approach | Comment 19 of 26 |
(In reply to re: New approach by Charlie)

Charlie - I wish I had a magic way to get the fraction.  All I did was carry out the calculation in excel to full decimal precision.  It is accurate to 13 or 14 decimals.  Consider it a guess.

btw, you get 1/2^5 + 2x211/2^10 + 3x9031/2^15 + 4x221551/2^20 + 5x4329151/2^25 + ...

 Posted by bernie on 2004-10-16 22:21:11

 Search: Search body:
Forums (0)
Random Problem
Site Statistics
Unsolved Problems
Top Rated Problems
This month's top
Most Commented On

Chatterbox: