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Subj:.....Multiplication (S667)
          From: MathNexus.wwu.edu
          on 1/11/2009
Drawing from MathNexus...

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Source: http://mathnexus.wwu.edu/Archive/problem/detail.asp?ID=150
 

The American Mathematics Contest 8 exam is designed for 
students in grades 6-8.  Based on the scores for the 2006 
exam, this problem was considered to be the "hardest" problem: 

    In the multiplication problem ABA x CD = CDCD, 
      where A, B, C, and D are different digits, 
                     what is A+B? 

What is your answer?

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Drawing from tom on 8/21/2009
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Hint: The problem actually was a multiple choice problem,
   where 15.39% of the students chose (A) 1, 16.15% chose
   (B) 2, 26.01% chose (C) 3, 17.68% chose (D) 4, 12.09% chose
   (E) 9, and 12.55% of the students did not answer the question.

Does this information help? 
 

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Finger pointing down
from darrell94590 on 1/2/2006
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Drawing from Ripleys-Believe It Or Not
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              THE SOLUTION
 

Solution Commentary: It is perhaps easier to turn the
   problem into a division problem: CDCD/CD = ABA.  Now CD
   "gozinta" CD** how many times...etc.

CD divides into CDCD 101 times.

This means that ABA is 101 and A + B = 1.

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