Question 1143739
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In the worst case, we should take all blue cards (2) and all green cards (3).


    2 + 3 = 5.


After taking the 6-th card we inevitably will have at least one red card,

and after taking the 7-th card we inevitably will have at least two red cards.


<U>ANSWER</U>.  After taking 7 (seven) cards we inevitably will have at least two red cards.
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