The probability that you get no six on first roll is 5/6. The probability that you get no sixes on two rolls is (5/6)(5/6). And in general the probability that you get no sixes on n rolls is (5/6)^n. Now if n=3 then that number is .578 (thus it islikelyyou get no sixes on 3 rolls), and if n=4 then that number is .482. Thus, it isunlikelyto get no sixes after 4 rolls. That number is 4.