Dayo chooses two digits at random, without replacement, from the 9-digit number 113 333 555.
The random variable \(X\) is the number of 5s that Dayo chooses. Draw up a table to show the probability distribution of \(X\).
Solution
To find the probability distribution of \(X\), we consider the possible values of \(X\): 0, 1, or 2.
Case 1: \(X = 0\)
This means no 5s are chosen. There are 6 non-5 digits (1s and 3s) and 3 5s. The probability of choosing two non-5s is:
\(P(0) = \frac{6}{9} \times \frac{5}{8} = \frac{30}{72} = \frac{5}{12}\)
Case 2: \(X = 1\)
This means one 5 is chosen. From part (ii), \(P(1) = 0.5\).
Case 3: \(X = 2\)
This means two 5s are chosen. From part (i), \(P(2) = \frac{6}{72} = \frac{1}{12}\).
The probability distribution table is:
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