self
Maths Puzzle
Years ago, to puzzle his friends, a scientist gave one of four containers containing blue and/or yellow marbles to each of the friends; Tom, Dick, Harry, and Sally.
There were 3 marbles in each container, and the number of blue marbles was different in each one. There was a piece of paper in each container telling which color marbles were in that container, but the papers had been mixed up and were ALL in the wrong containers.
He then told all of his friends to take 2 marbles out of their container, read the label, and then tell him the color of the third marble.
So Tom took two blue marbles out of his container and looked at the label. He was able to tell the color of the third marble immediately.
Dick took 1 blue marble and 1 yellow marble from his container. After looking at his label he was able to tell the color of his remaining marble.
Harry took 2 yellow marbles from his container. He looked at the label in his container, but could not tell what color the remaining marble was.
Sally, without even looking at her marbles or her label, was able to tell the scientist what color her marbles were. Can you tell what color marbles Sally had? Can you also tell what color marbles the others had, and what label was in each of their containers?
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self Other Question
Alex, Brook, Cody, Dusty, and Erin recently found out that all of their birthdays were on the same day, though they are different ages.
On their mutual birthday, they were jabbering away, flapping their gums about their recent discovery. And, lucky me, I was there. Some of the things that I overheard were...
* Dusty said to Brook: "I'm nine years older than Erin."
* Erin said to Brook: "I'm seven years older than Alex."
* Alex said to Brook: "Your age is exactly 70% greater than mine."
* Brook said to Cody: "Erin is younger than you."
* Cody said to Dusty: "The difference between our ages is six years."
* Cody said to Alex: "I'm ten years older than you."
* Cody said to Alex: "Brook is younger than Dusty."
* Brook said to Cody: "The difference between your age and Dusty's is the same as the difference between Dusty's and Erin's."
Since I knew these people -- and how old they were, I knew that they were not telling the whole truth.
After thinking about it, I realized that when one of them spoke to someone older, everything they said was true, but when speaking to someone younger, everything they said was false.
How old is each person?
You are about to leave for holiday, but you forgot socks! You race back to your room, but all the lights are off, so you can't see the color of the socks.
Never mind, because you remember that in your drawer there are ten pairs of white socks, ten pairs of black socks, and eleven pairs of blue socks, but they are all mixed up.
How many of your socks do you need to take before you can be sure to have at last one matching pair?