Find the last two digits of the following sum: 5! + 6! + 7! + 8! + 9! + 10! + ... + 100!
+592 Any factorial greater than 10! will end in 00. This means we just need to find what 5! + 6! + 7! + 8! + 9! ends in.
5! = 120
6! = 720
7! = 5040
8! = 40320
9! = 362880
Add up the last two digits of these numbers and you get 180, which means the last two digits of the sum is 80, which is your answer :)
