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Assuming the balls to be identical except for difference in colours, the number of ways in which one or more balls can be selected from 10 white, 9 green and 7 black balls is:
- 880
- 629
- 630
- 879
Correct answer: 879
Solution
Balls of each colour are identical, so selections = (10+1)(9+1)(7+1) - 1 = 11*10*8 - 1 = 880 - 1 = 879.
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