Ken's POTW 960813

FORTY + TEN + TEN = SIXTY

Each of the letters in the equation below represents one of the digits from 0 to 9. Determine which digit corresponds to each letter.

        FORTY
          TEN
        + TEN
        -----
        SIXTY

Source: Martin Gardner's Mathematical Diversions
[Taken from "Ken's Puzzle of the Day" February 28, 1994]

Ken's Solution:

Column 1: N is either 0 or 5. If N=5, then the carry to Col2 is 1 and there is no possible value for E, so N=0.
Column 2: E is ether 0 or 5, but N=0, so E=5, and the carry to Col3 is 1.
Column 4: I is either 0 or 1, but N=0, so I=1, O=9, carry from Col3 is 2, and the carry to Col5 is 1.
Column 3: For 1+R+T+T >= 20, R and T must be in {6,7,8}.
Column 5: F+1=S, so {F,S} is either {2,3} or {3,4}, so X is not 3.
Column 3: 1+R+T+T = 22 or 24, so R is odd and must be 7, 2T=14 or 16, T is 7 or 8, but R=7, so T=8, X=4.
Column 5: F=2, S=3.
Column 1: Y=6.

Denis Borris sent this solution:

What a delightful little puzzle.
Almost fully solvable by logic.

1-easy to see:                   F 9 R T Y
  N=0, E=5, O=9, I=1                 T 5 0
                                     T 5 0
                                 S 1 X T Y

2-also apparent:                 2 9 7 8 6
  S=F+1,so S/F=2/3/4,                8 5 0
  since R+T+T>19;                    8 5 0
  so, with minimun trial&error:  3 1 4 8 6

Solutions were also received from Ken Burres and Rick Simineo.

Mail to Ken