Why is 149 not divisble by 3?

Answer 1

One way to work it out in your head is to consider than 30 is divisible by 3, so you can ask if 140 is divisible by 30. It's not, since 14 is not divisible by 3. If the number was 129 or 159, both of those are divisible by three since both 12 and 15 are divisible by 3.