# Math Help - Probability and independence

1. ## Probability and independence

Let $Q_n$ denote the probability that in $n$ toss no heads comes up 3 times in a row. How do we show the probability of this happening?

2. Originally Posted by Scopur
Let $Q_n$ denote the probability that in $n$ toss
and the question is..

CB

3. Anyone ?
$Q_0 = Q_1 = Q_2 = 0$
$Q_3 = 7/8$ because the only possible outcome of 3 heads is $\{ H H H \}$Then i dont know how to do for Q_4

logically i thought it would be $14/16 = 7/8$ But what am i missing? i thought the only possibilities would be $\{ THHH, HHHT \}$