How to do this
The sum sigmai (x ! ) where x goes from 1 -100 ,is divided by 36, what is the remainder???ie 1! + 2! + 3! .......100!/36 gives wot remainder??
The prime decomposition of 36 is (2^2)(3^2). It appears for the fist time in 6! So, 6! onward, all factorials will be exactly divisible by 36. You need only check the remainder for (1! + 2! + 3! + 4! + 5!)/36, which is 9.
Locked
