Friday, 1 July 2011

The last ball

From the Futility Closet:

Posted in Puzzles by Greg Ross on June 30th, 2011
An urn contains 75 white balls and 150 black ones. A pile of black ones is also available.
The following two-step operation occurs repeatedly. First we withdraw two balls at random from the urn, then:
  • If both are black, we put one of them back in the urn and throw other away.
  • If one is black and the other white, we put the white one back and throw the black one away.
  • If both are white, we throw both away and put a black ball from the pile into the urn.
Because the urn loses a ball at each step, eventually it will contain a single ball. What color is that ball?
I will give the answer tomorrow.

I like these kind of riddles, Greg will post his answer tomorrow, meanwhile if you have no clue, see my guess here.

1 comment:

  1. "Last ball" refers to the final delivery in a sports match, particularly in cricket. It holds immense significance as it can determine the outcome of the game. Does Harm Games The tension and excitement surrounding the last ball make it a pivotal moment for players and fans alike, often deciding victory or defeat.



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