there are 6 red balls and 4 blue balls in a jar . if 3 balls are selected from the jar , what is the probability that all 3 balls selected are red balls ?
"the number of ways of choosing 3 balls from the jar is 10 c 3 = 120 . the number of ways of choosing 3 red balls is 6 c 3 = 20 . p ( 3 red balls ) = 20 / 120 = 1 / 6 . the answer is b ."
divide(choose(4, 3), choose(add(6, 4), 3))