Aisha chose a whole number and multiplied it by 3. Which of the following numbers could not be her answer?

Explanation

The very first solution that comes to our mind is the one that we learned in school. If the sum of digits in a number is a multiple of 3 then the number is a multiple of 3, e.g., for 612, the sum of digits is 9 so it's a multiple of 3. Here 1+0+3 equals 4 hence it is not a multiple of three, the others however are such 1+5 = 6 2+4= 6 4+4+4= 12 These are all divisible by 3 so are multiples of 3