QJEEM21Ma4e2c: JEE Main 2021 Mathematics - Class 12 JEEM21Ma4e2c Solution: A fair die is tossed until six is obtained on it. Let x be the…

Question

Verified Solution • 2025–26 Session moderate

A fair die is tossed until six is obtained on it. Let x be the number of required tosses, then the conditional probability P(x

\ge

5 | x > 2) is :

Accepted Answer

P(x

\ge

5 | x > 2) =

{{P(x \ge 5)} \over {P(x &gt; 2)}}

=

{{{{\left( {{5 \over 6}} \right)}^4}.{1 \over 6} + {{\left( {{5 \over 6}} \right)}^5}.{1 \over 6} + ....... + \infty } \over {{{\left( {{5 \over 6}} \right)}^2}.{1 \over 6} + {{\left( {{5 \over 6}} \right)}^3}.{1 \over 6} + ...... + \infty }}

=

{{{{{{\left( {{5 \over 6}} \right)}^4}.{1 \over 5}} \over {1 - {5 \over 6}}}} \over {{{{{\left( {{5 \over 6}} \right)}^2}.{1 \over 6}} \over {1 - {5 \over 6}}}}} = {\left( {{5 \over 6}} \right)^2} = {{25} \over {36}}

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