# Two balls selected from a box containing 2 blue and 7 red balls. What is the probability that at least one ball is blue? ?

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- AshLv 71 month ago
Another way of solving it....

P(at least 1 blue ball) = 1 - P(no blue balls)

P(no blue balls) = (₇C₂ * ₂C₀)/(₉C₂) = [7!/(2!*5!)]*1 /[9!/(2!*7!)] = 21/36 = 7/12

P(at least 1 blue ball) = 1 - (7/12) = 5/12

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