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Calendar Capers

Choose any three by three square of dates on a calendar page...

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Card Trick 2

Can you explain how this card trick works?

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Happy Numbers

Take any whole number between 1 and 999, add the squares of the digits to get a new number. Make some conjectures about what happens in general.


Stage: 3 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

Ann thought of 5 numbers and told Bob all the sums that could be made by adding the numbers in pairs. The list of sums is 6, 7, 8, 8, 9, 9, 10,10, 11, 12. Help Bob to find out which numbers Ann was thinking of.

[This is an exercise for practice from the Hungarian KöMaL magazine, September 2000 issue. You'll find many other challenging problems in English on the KöMaL website.]