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To find P(blue or medium), we need to add the probabilities of choosing a blue item and a medium item separately and then subtract the probability of choosing an item that is both blue and medium, since we don't want to double count it.
P(blue) = 6/30 = 1/5
P(medium) = 7/30
Out of the 30 total items, 1 is both blue and medium.
P(blue and medium) = 1/30
Therefore,
P(blue or medium) = P(blue) + P(medium) - P(blue and medium)
= 1/5 + 7/30 - 1/30
= 6/30 + 7/30 - 1/30
= 12/30
= 2/5
So, the probability of choosing an item that is either blue or medium is 2/5 or 12/30.