If the probability of hitting a target is $1/5$, and 10 shots are fired independently, what is the probability of the target being hit at least twice?
Let $X$ be the number of times the target is hit. We want to find $P(X \geq 2)$. So $$P(X \geq 2) = 1-P(X < 2)$$
$$ = 1- \binom{10}{0} (0.2)^{0} (0.8)^{10}-\binom{10}{1} (0.2)^{1}(0.8)^{9}$$
Would that be correct?
Thanks