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UKMT Senior Mathematical Challenge, 2009

Combinatorics Difficulty 2.0 Junior Find the answer United Kingdom

A bag contains hundreds of glass marbles, each one coloured either red, orange, green or blue. There are more than 2 marbles of each colour. Marbles are drawn randomly from the bag, one at a time, and not replaced. How many marbles must be drawn in order to ensure at least three marbles of the same colour are drawn?

(A) $4$ (B) $7$ (C) $9$ (D) $12$ (E) $13$

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