When a number is a multiple of 6 what are possible values of the ones digit

6,2,8,4, and 0 are the only possible value of the ones digit, because

6*1=6, last digit is 6

6*2=12, last digit is 2

6*3=18, last digit is 8

6*4=24, last digit is 4

6*5=30, last digit is 0

6*6=36, last digit is 6

and the whole cycle goes over again.