Puzzle for September 6, 2022  ( )

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Find the 6-digit number ABCDEF by solving the following equations:

eq.1) A + B + C + D + E + F = 25 eq.2) A + C = F eq.3) F - B = A + B eq.4) C + D = E eq.5) A + B + C + F = E eq.6) B + C + F = D

A, B, C, D, E, and F each represent a one-digit non-negative integer.

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Hint #1


In eq.5, replace B + C + F with D (from eq.6): eq.5a) A + D = E


  

Hint #2


In eq.5a, replace E with C + D (from eq.4): A + D = C + D Subtract D from each side of the above equation: A + D - D = C + D - D which makes A = C


  

Hint #3


In eq.2, substitute A for C: A + A = F which makes 2×A = F


  

Hint #4


Substitute 2×A for F in eq.3: 2×A - B = A + B In the equation above, add B to both sides, and subtract A from both sides: 2×A - B + B - A = A + B + B - A which becomes A = 2×B Divide both sides by 2: A ÷ 2 = 2×B ÷ 2 which makes ½×A = B


  

Hint #5


Substitute ½×A for B, A for C, and 2×A for F in eq.6: ½×A + A + 2×A = D which makes 3½×A = D


  

Hint #6


Substitute A for C, and 3½×A for D in eq.4: A + 3½×A = E which makes 4½×A = E


  

Solution

Substitute ½×A for B, A for C, 3½×A for D, 4½×A for E, and 2×A for F in eq.1: A + ½×A + A + 3½×A + 4½×A + 2×A = 25 which simplifies to 12½×A = 25 Divide both sides of the above equation by 12½: 12½×A ÷ 12½ = 25 ÷ 12½ which means A = 2 making B = ½×A = ½ × 2 = 1 C = A = 2 D = 3½×A = 3½ × 2 = 7 E = 4½×A = 4½ × 2 = 9 F = 2×A = 2 × 2 = 4 and ABCDEF = 212794