Unit digit of 1! + 2! + 3! + ……… 100! is ___________.

To find the unit digit of the sum of factorials from 1! to 100!, we need to understand a few things about factorials:

1. The factorial of a number is the product of all positive integers less than or equal to that number. For example, 5! = 54321 = 120.

2. The unit digit of the factorial of any number greater than 4 is always 0. This is because the factorial will involve multiplying by 2 and 5 (as part of 4!), which results in a trailing zero.

So, to find the unit digit of the sum of factorials from 1! to 100!, we only need to consider the factorials from 1! to 4!.

1! = 1 2! = 2 3! = 6 4! = 24

Adding these up, we get 1 + 2 + 6 + 4 = 13.

So, the unit digit of the sum of factorials from 1! to 100! is 3.