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Question 331009: If you multiply this odd digit by itself, the sum of the digits of the product is 7. What is the mystery digit? and how.
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! If you multiply this odd digit by itself, the sum of the digits of the product is 7. What is the mystery digit? and how.
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It's 5.
If the sum of the digits of the square = 7, the number has to be small.
Try the odd numbers - 1, 3, 5... 5 works.
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49 also works.
149 also works.
1049 also works.
Probably some others.
Not a well presented problem, it should ask for the smallest odd number that fits.
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