Question

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

• A. 7
• B. 5
• C. 3!
• D. 17!

Answer 1

Answer: (C)

$1!=1\Rightarrow$ ten's digit = 0
$4!=24\Rightarrow$ ten's digit = 2
$7!=5040\Rightarrow$ ten's digit = 4
Now, $10!,12!,13!,15!,16!$ and $17!$ have ten's digit = 0
Hence, ten's digit of $1!+4!+7!+10!+12!+13!+15!+16!+17!$ is $0+2+4+0=6$ which is divisible by $3!$.