Puzzle for August 8, 2022  ( )

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

eq.1) A + B + C + D + E + F = 20 eq.2) B = D + F eq.3) C + F = B – C eq.4) D = A + C eq.5) E = B + F eq.6) F = A + D

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

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Hint #1


In eq.3, replace B with D + F (from eq.2): C + F = D + F – C In the above equation, subtract F from both sides, and add C to both sides: C + F – F + C = D + F – C – F + C which makes 2×C = D


  

Hint #2


In eq.4, replace D with 2×C: 2×C = A + C Subtract C from each side of the equation above: 2×C – C = A + C – C which makes C = A


  

Hint #3


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


  

Hint #4


Substitute 2×C for D, and 3×C for F in eq.2: B = 2×C + 3×C which makes B = 5×C


  

Hint #5


Substitute 5×C for B, and 3×C for F in eq.5: E = 5×C + 3×C which makes E = 8×C


  

Solution

Substitute C for A, 5×C for B, 2×C for D, 8×C for E, and 3×C for F in eq.1: C + 5×C + C + 2×C + 8×C + 3×C = 20 which simplifies to 20×C = 20 Divide both sides of the above equation by 20: 20×C ÷ 20 = 20 ÷ 20 which means C = 1 making A = C = 1 B = 5×C = 5 × 1 = 5 D = 2×C = 2 × 1 = 2 E = 8×C = 8 × 1 = 8 F = 3×C = 3 × 1 = 3 and ABCDEF = 151283