Question

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

Answer 1

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.