Question

If the number 481 * 673 is completely divisible by 9, then the smallest whole number in place of * will be:

Answer 1

 if number is divisible by 9, then the sum of the numbers must be divisible by 9.
sum of numbers except * = 4+8+1+6+7+3 = 29
so the sum should be 36.
* = 36-29 = 7

So 7 will be there in place of *. 

Answer 2

the divisibility test for 9 states that the sum of all digits of the number should be divisible by 9.
here 4+8+1+6+7+3=29
the next number divisible by 9 is36.
so the number which goes in the blank place is 36-29=7