Question

Find the smallest value of 'a' if 3a9 is divisible by 9.

• A. 2
• B. 4
• C. 6
• D. 8

Answer 1

The correct option is C

6

For a number to be divisible by 9, sum of the digits of the 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 smallest multiple of 9 greater than 12 is 18.

Therefore, 12 + a = 18
a = 18 - 12 = 6

Therefore, the smallest value of a which will make 3a9 divisible by 9 is 6.