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Question
A die is thrown again and again until three sixes are obtained. Find the probability of obtaining the third six in the sixth throw of the die.
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Solution
The probability of getting a six in a throw of die 1/6 and not getting a six is 5/6.
Let `p = 1/6 and q = 5/6`
The probability that the 2 sixes come in the first five throws of the die is `""^5C_2 (1/6)^2(5/6)^3 = (10xx(5)^3)/(6)^5 `
∴ Probability that third six comes in the sixth throw `(10xx(5)^3)/(6)^5 xx 1/6`
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