1- A box contains m red and n white balls. If 4 balls are drawn at random withou

Question

1- A box contains m red and n white balls. If 4 balls are drawn at random without replacement, what is the probability that 2 of them are red? 2- A box contains m red and n white balls. If 4 balls are drawn at random with replacement, what is the probability that 2 of them are red? 3- A box contains m red and n white balls. If balls are drawn at random without replacement, what is the probability that the first red ball will be drawn in the fifth trial? 4- A box contains m red and n white balls. If balls are drawn at random with replacement, what is the probability that the first red ball will be drawn in the fifth trial?

Explanation / Answer

1) P(2 of them are red) = mC2 * nC2 / m+nC4

2) P(2 of them are red) = 4C2 * (m / (m+n))2 * (n / (m+n))2

3) P(first red ball will be drawn in the fifth trial) = (nC4 * m) / (m+nC4 * (m+n-4))

4) P(first red ball will be drawn in the fifth trial) = (n / (m+n))4 * (m / (m+n))

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