Q) 7 white balls & 3 black balls are randomly placed in a row. Find the probability that no two black balls are placed adjacently.

A)
First fix the seven white balls, then you have eight places for the black balls to choose from... and 8C3 is the number of combinations you can have ( how the places are chosen)
Total number of arrangements of the 10 balls is 10C3
So prob = 8C3 / 10C3 = 7/15

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