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Total number of balls = 4 + 2 + 5 = 11 (this is our denominator for first draw)Numerator is the number of each colour. When we remove a ball the denominator and numerator for that colour decrease by 1. P(2 blue) = (4/11)(3/10) = (12/110), P(2 red) = (2/11)(1/10) = (2/110), P(2 green) = (5/11)(4/11) = (20/110)To find the total probability of picking two of the same colour we add these probabilities together then simplify.Total probability = 12/110 + 2/110 + 20/110 = 34/110 = 17/55