Question

${10}^n+3(4^{n+2})+5$ is divisible by $(n\in N)$ :

• A. 7
• B. 5
• C. 9
• D. 17
• E. 13

Answer 1

Answer: (C)

For $n=1,{10}^n+{3.4}^{n+2}+5$
$=10+{3.4}^3+5=10+192+5$
$=207$
which is divisible by 9.
$\therefore$ By Induction, the result is divisible by 9.