Puzzler #1
The iChat team asked me this one:
You have 10 balls, 5 black and 5 green. There are two sacks into which all the balls must be placed. You place the balls in the sacks (snigger), and then a ball is chosen from a sack at random.
How can you arrange the balls in the sacks to provide the best probability that a black ball will be chosen?
Click below to see the answer.
ANSWER:
Put one black ball in one sack and the other 9 in the other sack. The one ball will give a 50% chance of picking black, right off the bat. The other sack will be (4/9)% of the remaining 50%, for a total of just under 75%.
I got that one right away; I was rather pleased with myself.