What digit(s) can be in the ones place of a number that has 5 as a factor?

Answer 1

Multiples of 5 (beginning at 5) are 5, 10, 15, 20, 25, 30, 35, ...

Notice, of course, all multiples of 5 are divisible by 5 and their pattern shows that their ones digit alternates between 0 and 5.