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Archive for August, 2012

Frank and Tank (and the money safe game)

Posted by DP under Logic, Tom (10 Responds)

Frank and Tank, who are twin brothers, have invited 5 men to play a new game they have created. Andy, Bob, Charlie, Dave, and Eddy have agreed to play after hearing Frank explain the following:
In a small room, behind closed doors, a very large sum of money will be randomly placed into one of 5 [...]

Black or White 3

Posted by Chris under Logic (13 Responds)

John provided the following problem on a comment on the “Black or White” page:
There are a number of cards in a hat, 20% of which are white on both sides, 50% of which are black on one side and white on the other and 30% of which are black on both sides.
One card is drawn [...]

Yet another prime problem

Posted by Chris under MathsChallenge (15 Responds)

Find three different prime numbers between 10 and 99, where the average of any two is a prime and the average of all three is a prime.
Obviously no computers and minimal trial and errror only.

123456

Posted by Chris under Mathemagic (7 Responds)

What is the smallest factor of 123456! + 1?
That number is approximately 2.6 * 10574964

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