three unbiased coins are tossed . what is the probability of getting at most two heads ?
explanation : here s = { ttt , tth , tht , htt , thh , hth , hht , hhh } let e = event of getting at most two heads . then e = { ttt , tth , tht , htt , thh , hth , hht } . p ( e ) = n ( e ) / n ( s ) = 7 / 8 . answer is d
negate_prob(divide(const_1, power(const_2, const_3)))