How do I solve this problem regarding divisibility from my Math Challenge class?

Question

1. Which of the following numbers is divisible by 2 and 3, but not divisible by 4?
2. 3346
3. 2376
4. 5554
5. 3282
6. 9996

Answer 1

3282

To determine divisibility by 4 just look at the last 2 digits as 100 is a multiple of 4. 82 is not a multiple of 4. Every even number is a multiple of 2.

To determine divisibility by 3, add all the digits; If your sum is a multiple of 3, the original number is divisible by 3. 3 + 2 + 8 + 2 = 15, so 3282 is divisible by 3.