Probability 1 Question 2
2. In a random experiment, a fair die is rolled until two fours are obtained in succession. The probability that the experiment will end in the fifth throw of the die is equal to
(a)
(b)
(c)
(d)
(2019 Main, 12 Jan I)
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Answer:
Correct Answer: 2. (a)
Solution:
- Since, the experiment should be end in the fifth throw of the die, so total number of outcomes are
Now, as the last two throws should be result in two fours (i)
So, the third throw can be 1, 2, 3, 5 or 6 (not 4). Also, throw number (i) and (ii) can not take two fours in succession, therefore number of possibililites for throw (i) and (ii)
Hence, the required probability
