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A 3 digit number 
20080123 

From Adrian: Consider a 3digit number,abc,where a is not equal to c.Switch it so that it becomes cba.Subtract
the lesser from the greater to obtain rst.Switch this so that it is tsr.Prove that rst+tsr=1089 Answered by Stephen La Rocque. 





Write the digits 1 to 9 on index cards, ... 
20061019 

From Kim: Write the digits 1 to 9 on index cards, arrange the cards to form three 3digit numbers (using each card only ONCE). The third number is the sum of the first two numbers ** how many different ways can you do this?? ** Answered by Penny Nom. 


