How can you tell if 1245 is divisible by3 and by 0?

First check if the first two digits are divisible by 3 (45 / 3 = 15 So yes it is) And then if the first two are divisible by 3, then check if the next two are divisible by three, (12 / 3 = 4) Yes, so if both are, then yes the answer is divisible by three.