There isn't much I can add to the question description to expand upon the title. I came across this in a multiple choice test. The options were $3$, $0$, $1$ and $7$. I am absolutely stumped. Any pointers? By the way I ran a computer program and the answer is $3$. The rest of the test was quite easy, apparently I am missing something obvious.
2026-04-07 11:34:57.1775561697
Digit in units place of $1!+2!+\cdots+99!$
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Hint: If $n\geq 5$, what is the last digit of $n!$ ?