NDA 2021 Mathematics question

Seven white balls and three black balls are randomly placed in a row. What is the probability that no two black balls are placed adjacently?

(A)Correct
(B)
(C)
(D)

Answer: (A)

Solution

Treat balls of the same colour as alike. Total arrangements number of ways of choosing 3 positions out of 10 for the black balls . For no two black balls to be adjacent, first place the 7 white balls; they create 8 gaps

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Question ID VK-033731