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MathNet 2011 Question 84

Math Olympiad Vault · MathNet 2011

Question 84

In an urn there are $100$ balls each coloured either blue, red or green. If you draw (without repetitions) two balls randomly from the urn, the probability of getting two balls of different colour is $58\%$, and the probability of getting a blue and a green ball is $8\%$. How many red balls are there among the $100$ balls?