Question

$3a9$ is divisible by 9 if the digit ${}^{\prime }{a}^{\prime }$ is equal to:

• A. 2
• B. 4
• C. 6
• D. 8

Answer 1

The correct option is C

6

For the number to be divisible by 9 the sum of digits of number must be a multiple of 9.
Sum of the digits of $3a9=3+a+9=12+a$

$12+a$ should be a multiple of 9 to satisfy the condition. The nearest multiple of 9 next to 12 is 18.

Therefore, $12+a=18$

So, $a=18-12=6$