isi-entrance 2015 Q21

isi-entrance · India · UGB 4 marks Number Theory Properties of Integer Sequences and Digit Analysis

The digit in the units' place of the number $1 ! + 2 ! + 3 ! + \ldots + 99 !$ is
(a) 3
(b) 0
(c) 1
(d) 7.

(a) The unit digit of all numbers $n !$ with $n \geq 5$ is 0.

The digit in the units' place of the number $1 ! + 2 ! + 3 ! + \ldots + 99 !$ is\\
(a) 3\\
(b) 0\\
(c) 1\\
(d) 7.