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Apr 3, 2017
 #5
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My proffesor gave me this to problem to resolve it, but I really do not know how to do this 

8444...4...455= divisible to 19

Between the 8 and the two 5 are 2017 fours

 

8444...4...455 is divisible to 19, if 8444...4...455 modulo 19 = 0

 

  • We calculate 8444...4...455 modulo 19:
    We divide 8444...4...455 in parts of 3-digits. ( The partition is arbitrary ).
    But the first part is 8444.

So the Number is:

\(\begin{array}{lcll} \underbrace{8444}_{\text{ Fist Part }}\ \underbrace{444}_{\text{ Second Part }}\ 444\ 444\ 444\ 444\ 444\ 444\ 444\ \ldots \underbrace{444}_{\text{ Part 672 }} \ \underbrace{455}_{\text{ Last Part }} \qquad \text{2017 fours} \\ \end{array} \)

 

\(\begin{array}{|rcll|} \hline && \text{first part} \pmod {19} \\ &\equiv& 8444\pmod {19}\\ &=& \color{red}8 \color{black}\qquad (8444=444\cdot 19 + \color{red}8 \color{black}) \\\\ && \text{The last remainder } = \color{red}8 \\ \hline \end{array} \)

 

\(\begin{array}{|rcll|} \hline && \text{Second part} \pmod {19} \\ &\equiv& \underbrace{8}_{\text{ The last remainder }}\underbrace{444}_{\text{ Second part }}\pmod {19}\\ &=& \color{red}8 \color{black}\qquad (8444=444\cdot 19 + \color{red}8 \color{black}) \\\\ && \text{The new last remainder } = 8 \\ \hline \end{array} \)

 

\(\cdots \)

 

\(\begin{array}{|rcll|} \hline && \text{Part 672} \pmod {19} \\ &\equiv& \underbrace{8}_{\text{ The last remainder }}\underbrace{444}_{\text{ Part 672 }}\pmod {19}\\ &=& \color{red}8 \color{black}\qquad (8444=444\cdot 19 + \color{red}8 \color{black}) \\\\ && \text{The new last remainder } = 8 \\ \hline \end{array}\)

\(\begin{array}{|rcll|} \hline && \text{Last part} \pmod {19} \\ &\equiv& \underbrace{8}_{\text{ The last remainder }}\underbrace{455}_{\text{ Last part }}\pmod {19}\\ &=& \color{red}0 \color{black}\qquad (8455=445\cdot 19 + \color{red}0 \color{black}) \\\\ && \text{The new last remainder } = 0 \\ \hline \end{array} \)

 

8444...4...455 is divisible to 19, because 8444...4...455 modulo 19 = 0

 

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Apr 3, 2017
 #4
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Apr 3, 2017
 #1
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Apr 3, 2017

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