Question

The ten's digit in $1! + 4!+ 7! + 10!+12! + 13! + 15! +16! + 17!$ is divisible by

• A. 4
• B. 3!
• C. 5
• D. 7

Answer 1

Answer: (B)

3!

Answer 2

As we know the last two digits of $10 !$ and above factorials will be zero- zero. $\therefore 1 !+4 !+7 !+10 !+12 !+13 !+15 !+16 !+17 !$ $=1+24+5040+10 !+12 !+13 !+15 !+16 !+17 !$ $=5065+10 !+12 !+13 !+15 !+16 !+17 !$ In this series, the digit in the ten place is $6$ which is divisible by $3 !$