Explanation:
24 times, as there are no orange marbles in the set.
so, every pull will produce a marble that is not orange with 100% certainty.
in general, we have 12 marbles.
let's change the problem description into picking a marbles that is not blue.
we have 6 blue marbles.
the chance to pick a blue marble is therefore 6/12 = 1/2.
and the probability to not pick a blue marbles is 1 - 1/2 = 1/2.
so, in 24 pulls, we expect 24× 1/2 = 12 times to get a marble that is not blue.
or change it to "not green" marbles.
5 green marbles.
the probability to pick a green marble is 5/12.
the probabilty to not pick a green marble = 1 - 5/12 = 7/12.
in 24 pulls we expect 24 × 7/12 = 14 times to get a marble that is not green.
it change it to "not purple" marbles.
1 purple marble.
the probability to pick a purple marble is 1/12.
the probabilty to not pick a purple marble = 1 - 1/12 = 11/12.
in 24 pulls we expect 24 × 11/12 = 22 times to get a marble that is not purple.