If a four-digit number $$5A2A$$ can be divisible by $20$, the digit that $$A$$ represents is  . 
Overseas Competition->Knowledge Point->Number Theory Modules->Division without Remainders->Divisibility Rules
We consider the last two-digit to see if a number is divisible by $4$. We consider the last one digit to see if a number is divisible by $5$. If $$\overline{\textasciitilde5A2A\textasciitilde}$$ is divisible by $5$, the ones digit can only be $5$ or $0$. When the ones digit is $0$, the number that is formed by the last two digits, $20$, is divisible by $4$. 