Puzzle for October 18, 2022  ( )

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

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

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

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Hint #1


Add F to both sides of eq.2: D - F + F = B + E + F which becomes D = B + E + F which may be written as D = B + F + E In the above equation, replace B + F with E (from eq.1): D = E + E which makes eq.2a) D = 2×E


  

Hint #2


In eq.6, replace D with 2×E: 2×E = E × F Divide both sides of the above equation by E: 2×E ÷ E = E × F ÷ E which makes 2 = F


  

Hint #3


In eq.5, substitute 2 for F: E = B × 2 which may be written as eq.5a) E = 2×B


  

Hint #4


Substitute 2×B for E, and 2 for F in eq.1: 2×B = B + 2 Subtract B from each side of the equation above: 2×B - B = B + 2 - B which makes B = 2


  

Hint #5


Substitute 2 for B in eq.5a: E = 2×2 which makes E = 4


  

Hint #6


Substitute 4 for E in eq.2a: D = 2×4 which makes D = 8


  

Hint #7


Substitute 2 for F and B in eq.3: A + 2 = 2 + C Subtract 2 from each side of the above equation: A + 2 - 2 = 2 + C - 2 which makes A = C


  

Solution

Substitute 8 for D, 2 for F, and A for C in eq.4: 8 + 2 = A + A - 8 which becomes 10 = 2×A - 8 Add 8 to both sides of the equation above: 10 + 8 = 2×A - 8 + 8 which makes 18 = 2×A Divide both sides by 2: 18 ÷ 2 = 2×A ÷ 2 which makes 9 = A and also makes A = C = 9 and makes ABCDEF = 929842