Modular Arithmetic
(a) How many positive integers from 1 to 5000 satisfy the congruence \(N\equiv5\pmod{12} \)?
\(\begin{array}{|lrcll|} \hline N\equiv5\pmod{12} & \text { or } & N-5 &=& n\cdot 12 \\ & & N &=& n\cdot 12 + 5 \quad & | \quad N_{max} = 5000 \\ & & 5000 &=& n\cdot 12 + 5 \\ & & n &=& \frac{5000-5}{12} \\ & & n &=& [416].25 \\\\ \mathbf{n=416} &\Rightarrow& N &=& 416\cdot 12 + 5 = 4997 \\ \hline \end{array}\)
416 + 1(n=0) = 417 positive integers from 1 to 5000 satisfy the congruence \(N\equiv5\pmod{12}\)
(b) How many positive integers from 1 to 5000 satisfy the congruence \( N\equiv11\pmod{13}\) ?
\(\begin{array}{|lrcll|} \hline N\equiv11\pmod{13} & \text { or } & N-11 &=& n\cdot 13 \\ & & N &=& n\cdot 13 + 11 \quad & | \quad N_{max} = 5000 \\ & & 5000 &=& n\cdot 13 + 11 \\ & & n &=& \frac{5000-11}{13} \\ & & n &=& [383].769230769 \\\\ \mathbf{n=383} &\Rightarrow & N &=& 383\cdot 13 + 11 = 4990 \\ \hline \end{array}\)
383 + 1(n=0) = 384 positive integers from 1 to 5000 satisfy the congruence \(N\equiv11\pmod{13}\)
The answer is wrong, I tried those answers before too. IDK why it won't work...