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Eduncle Best Answer
The probability that 1st ball is of 1 colour = 3/12
2nd ball also of same colour without replacement = 2/11
3rd ball of same colour without replacement = 1/10
Total probability = P (A & B & C) 3/12 × 2/11 × 1/10 = 6/1320
Since there are 3 others colours (each having same no. of balls mixed). All of the individual probabilities need to be added up . The reason this has to be done is because they have not mentioned any particular colour of ball to be picked.
i.e. 6/1320 + 6/1320 + 6/1320 + 6/1320 = 24/1320 = 1/55