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HKIMO 2018 THPT (Grades 10–12 shared) National Final (Heat) Set 03 Question 5

HKIMO · HKIMO 2018 THPT (Grades 10–12 shared) National Final (Heat) Set 03

Question 5

A box has 17 red,13 white and 16 blue socks. How many random draws guarantee 2 non-red pairs and 3 non-blue pairs?

Convention: pairs consist of two same-colour socks; all five selected pairs are disjoint.