Question

find the units digit sum of 1!+2!+3!+4!+.......+2005;! ​

Answer 1

Step-by-step explanation:

N=1!+2!+.....+2005!

=(1!+2!+3!+4!)+(5!+.....+2005!)

=33+ an integer having 0 in its unit's place

= an integer having 3 in its unit's place

By examining the unit digits of 3 powers, N

500

is an integer having 1 in its unit's place.

Answered By