Challenge Level

Digits add up to a multiple of 3

3 + 4 = 7 (at least one of each)

Adding more 3s will not help get closer to a multiple of 3

3 + 4 + 4 = 11

3 + 4 + 4 + 4 = 15

Smallest possibility: 3444

44 is divisible by 4 so 3444 is divisible by 4

This problem is taken from the UKMT Mathematical Challenges.

You can find more short problems, arranged by curriculum topic, in our short problems collection.