Seven white balls and three black balls are randomly placed in a row. Find the probability that no two black balls are placed adjacently to each other.  Choose the correct choice from the following choices:
A) 7/15  B) 2/15  C) 3/7  D) 2/7  E) 1/7
The total ways of placing seven white balls and three black balls in a row = 10! / 7! / 3! = 120.   The number of ways in which no two black balls are placed next to each other:   Assume that seven white balls are placed in a continuous line with gaps before and after each ball. There are totally 8 such gaps. Out of these 8 gaps, 3 gaps should be chosen in order to place the black balls. There are a total of 8C3 = 56 ways in which this can be done.   Hence, the required probability = 56/120 = 7/15.   7/15NSWER:7/15
<result>A</result>
Seven white balls and three black balls are randomly placed in a row. Find the probability that no two black balls are placed adjacently to each other.