Question 1189328
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Sorry -- in my original response I had the numbers of white and black balls switched.  Here are the corrected calculations:<br>
(1) Total number of ways of choosing 3 of the 5+7=12 balls: C(12,3)<br>
(2) Number of ways of choosing all 3 white (and 0 black): C(5,3)*C(7,0) (not C(7,3)*C(5,0))<br>
(3) Number of ways of choosing 2 white and 1 black: C(5,2)*C(7,1) (not C(7,2)*C(5,1))<br>
(4) Number of ways of choosing all 3 white OR all 3 black: C(7,3)*C(5,0) + C(7,0)*C(5,3)<br>
Note in the above calculations that "and" means the numbers of ways are multiplied, while "or" means the numbers of ways are added.<br>
ANSWERS:
a) (2) divided by (1)
b) (3) divided by (1)
c) (4) divided by (1)<br>
You can do the calculations