288 is completely divisible by__________.
9
Let's verify each option to find the correct answer.
288 is not divisible by 5 because it doesn't end with 5 or 0.
288 is not divisible by 11 because the difference between the sums of odd and even places is not 0 or multiple of 11.
288 is not divisible by 7 as it doesn't satisfy the divisibility rule of 7.
288 is divisible by 9 as the sum of the digits 2+8+8 = 18 is divisible by 9.