Puzzle for September 28, 2020  ( )

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

eq.1) A + B + C + D + E + F = 27 eq.2) C + D = B – C eq.3) B = D + F eq.4) A = C + F eq.5) D = A + C + F eq.6) E = C + D

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

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Hint #1


Add C to both sides of eq.2: C + D + C = B – C + C which becomes 2×C + D = B In eq.3, replace B with 2×C + D: 2×C + D = D + F Subtract D from each side of the above equation: 2×C + D – D = D + F – D which makes 2×C = F


  

Hint #2


In eq.4, replace F with 2×C: A = C + 2×C which makes A = 3×C


  

Hint #3


In eq.5, substitute 3×C for A, and 2×C for F: D = 3×C + C + 2×C which makes D = 6×C


  

Hint #4


Substitute 6×C for D, and 2×C for F in eq.3: B = 6×C + 2×C which makes B = 8×C


  

Hint #5


Substitute 6×C for D in eq.6: E = C + 6×C which makes E = 7×C


  

Solution

Substitute 3×C for A, 8×C for B, 6×C for D, 7×C for E, and 2×C for F in eq.1: 3×C + 8×C + C + 6×C + 7×C + 2×C = 27 which simplifies to 27×C = 27 Divide both sides of the equation above by 27: 27×C ÷ 27 = 27 ÷ 27 which means C = 1 making A = 3×C = 3 × 1 = 3 B = 8×C = 8 × 1 = 8 D = 6×C = 6 × 1 = 6 E = 7×C = 7 × 1 = 7 F = 2×C = 2 × 1 = 2 and ABCDEF = 381672