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HKIMO 2019 THPT (Grades 10–12 shared) National Final (Heat) Set 02 Question 5

HKIMO · HKIMO 2019 THPT (Grades 10–12 shared) National Final (Heat) Set 02

Question 5

A box contains 22 red,36 white and 25 blue socks. How many random draws guarantee 3 non-white pairs and 1 non-blue pair?

Convention: a pair uses two socks of the same colour, and the requested pairs do not share socks.