2 ms·
Use the test for divisibility by 3: if the sum of the digits is divisible by 3, the number is divisible by 3. 5+1=6, so 51 is divisible by 3.
by jemfinch 11y ago
Use the test for divisibility by 3: if the sum of the digits is divisible by 3, the number is divisible by 3. 5+1=6, so 51 is divisible by 3.
- noobie 11y agoOh yeah, that's what I meant by saying "up until you add the digits and it's clear of course.". It's just an instant observation I guess.