Question 748390

I'm pretty good at probability, but can't figure this problem out. I can't find my notes and am reviewing for an exam!
 "If a teacher has a box of 10 expo markers and only half of them work, what is the probability that at least one of 3 randomly selected markers works?"


Binomial probability formula: {{{_[n]C[s] * p^s * q^(n-s)}}}    


At least 1 of 3 means either 1, 2, or 3 will work, or P(1, 2, or 3), or P(1) + P(2), or P(3)


P(1) = 0.010


P(2) = 0.044


P(3) = 0.117 


Probability that at least 1 of 3 will work = P(1) + P(2) + P(3), or 0.010 + 0.044 + 0.117, or {{{highlight_green(.171)}}}, or {{{highlight_green(17.1)}}}%.