Question

If x = remainder when( 1! + 2! + 3! + + 100! ) is divided by 15. Find x.

Answer 1

Answer:

5! is divisible by 15  

n! will be divisible by 15 if n≥5  

1! + 2! + 3! + 4!  

= 1 + 2 + 6 + 24  

= 33  

33 = 15×2 + 3  

The remainder will be 3  

n  

Σi!   = 15a + 3 if n≥5  

i=1

Answer 2

x is 7.06666667 because 1+2+3+100=106/15=7.06666667