If two coins are tossed there are four possibilities of the result as follows :

(H -H ) , (H -T ) , (T -H ) & (T -T ) hence there are 4 total outcomes . At least one tail means there are 3 such favorable results possible that is (H -T ) , (T -H ) & (T -T )

Probability of getting at least one tail = Number of favorable results / Total possible results = 3/4

Answer : 3/4

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