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What is the units digit of 11!
- Thread starter brucejin
- Start date
What is the units digit of 11!
What is the units digit of 21!
Zero.
Any factorial greater than 10! will have 10 as a factor. That will guarantee a 0 on the end.
Actually, I don't think you need to go past 5! to have a units digit of 0...
1! = 1
2! = 2*1 = 2
3! = 3*2*1 = 6
4! = 4*3*2*1 = 24
5! = 5*4*3*2*1 = 120
5! ends in 0, right?
Now, any factorial LARGER than 5! will be SOMETHING * 5!, and that's going to end in 0.
1! = 1
2! = 2*1 = 2
3! = 3*2*1 = 6
4! = 4*3*2*1 = 24
5! = 5*4*3*2*1 = 120
5! ends in 0, right?
Now, any factorial LARGER than 5! will be SOMETHING * 5!, and that's going to end in 0.