A video game rewards players who have won a challenge with a randomly drawn object. The drawn object can be ``common'' or ``rare''. Two types of objects, common or rare, are available: swords and shields. The video game designers have planned that:
the probability of drawing a rare object is $7\%$;
if a rare object is drawn, the probability that it is a sword is $80\%$;
if a common object is drawn, the probability that it is a sword is $40\%$.
Part B A player wins 30 challenges. We denote $X$ the random variable corresponding to the number of rare objects the player obtains after winning 30 challenges. The successive draws are considered independent.
Determine, by justifying, the probability distribution followed by the random variable $X$. Specify its parameters, as well as its expected value.
Determine $P(X < 6)$. Round the result to the nearest thousandth.
Determine the largest value of $k$ such that $P(X \geqslant k) \geqslant 0.5$. Interpret the result in the context of the exercise.
The video game developers want to offer players the option to buy a ``gold ticket'' which allows them to draw $N$ objects. The probability of drawing a rare object remains $7\%$. The developers would like that by buying a gold ticket, the probability that a player obtains at least one rare object in these $N$ draws is greater than or equal to $0.95$. Determine the minimum number of objects to draw to achieve this objective. Care should be taken to detail the approach used.
A video game rewards players who have won a challenge with a randomly drawn object. The drawn object can be ``common'' or ``rare''. Two types of objects, common or rare, are available: swords and shields.
The video game designers have planned that:
\begin{itemize}
\item the probability of drawing a rare object is $7\%$;
\item if a rare object is drawn, the probability that it is a sword is $80\%$;
\item if a common object is drawn, the probability that it is a sword is $40\%$.
\end{itemize}
\textbf{Part B}
A player wins 30 challenges. We denote $X$ the random variable corresponding to the number of rare objects the player obtains after winning 30 challenges. The successive draws are considered independent.
\begin{enumerate}
\item Determine, by justifying, the probability distribution followed by the random variable $X$. Specify its parameters, as well as its expected value.
\item Determine $P(X < 6)$. Round the result to the nearest thousandth.
\item Determine the largest value of $k$ such that $P(X \geqslant k) \geqslant 0.5$. Interpret the result in the context of the exercise.
\item The video game developers want to offer players the option to buy a ``gold ticket'' which allows them to draw $N$ objects. The probability of drawing a rare object remains $7\%$. The developers would like that by buying a gold ticket, the probability that a player obtains at least one rare object in these $N$ draws is greater than or equal to $0.95$.\\
Determine the minimum number of objects to draw to achieve this objective. Care should be taken to detail the approach used.
\end{enumerate}