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A number well defined (Posted on 2018-10-25) Difficulty: 3 of 5
Half of my 2-digit number N is also a 2-digit number,
one of its digit being the sum of N's digit, the other their difference.
All 4 digits are different.

Find my number.

No Solution Yet Submitted by Ady TZIDON    
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Solution Algebraic Solution | Comment 2 of 5 |
Let N = 10a + b
Let N/2 = 10c + d
Then 10a + b = 20c + 2d

c cannot be the sum of the digits, so d = a + b

Then 8a - b = 20c

If c = a - b, then this becomes 19 b = 12a, and the only solution in single digits is (0,0).

So c = b - a.

Then 28a = 21b
          4a =  3b
Solution = (3,4)

N = 34 and N/2 = 17.  Only solution
  

  Posted by Steve Herman on 2018-10-25 09:33:06
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