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JEE Advanced 2022 · Probability (Class 11)

Two players, P1P_1 and P2P_2, play a game against each other. In every round of the game, each player rolls a fair die once, where the six faces of the die have six distinct numbers. Let xx and yy denote the readings on the die rolled by P1P_1 and P2P_2, respectively. If x>yx > y, then P1P_1 scores 5 points and P2P_2 scores 0 point. If x=yx = y, then each player scores 2 points. If x<yx < y, then P1P_1 scores 0 point and P2P_2 scores 5 points. Let XlX_l and YlY_l be the total scores of P1P_1 and P2P_2, respectively, after playing the lthl^{\text{th}} round. | List-I | List-II | | --- | --- | | (I) Probability of (X2≥Y2)(X_2 \geq Y_2) is | (P) 38\frac{3}{8} | | (II) Probability of (X2>Y2)(X_2 > Y_2) is | (Q) 1116\frac{11}{16} | | (III) Probability of (X3=Y3)(X_3 = Y_3) is | (R) 516\frac{5}{16} | | (IV) Probability of (X3>Y3)(X_3 > Y_3) is | (S) 355864\frac{355}{864} | | | (T) 77432\frac{77}{432} | The correct option is:

Answer: A. (I) →\to (Q); (II) →\to (R); (III) →\to (T); (IV) →\to (S)

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Written solution

Two players, P₁ and P₂, play a game against each other. In every round of the game, each player rolls a fair die once, where the six faces of the die have six distinct numbers. Let x and y denote the readings on the die rolled by P₁ and P₂, respectively. If x > y, then P₁ scores 5 points and P₂ scores 0 point. If x = y, then each player scores 2 points. If x < y, then P₁ scores 0 point and P₂ scores 5 points. Let Xₗ and Yₗ be the total scores of P₁ and P₂, respectively, after playing the lᵗᵉˣ

x>y⇒P1:5, P2:0x>y \Rightarrow P_1:5,\ P_2:0

x=y⇒2 eachx=y \Rightarrow 2 \text{ each}

x<y⇒P1:0, P2:5x<y \Rightarrow P_1:0,\ P_2:5

To find: the correct matching option\text{To find: the correct matching option}

P(x>y)=1536=512 (=p)P(x>y) = \dfrac{15}{36} = \dfrac{5}{12} \ (=p)

P(x=y)=636=16 (=r)P(x=y) = \dfrac{6}{36} = \dfrac{1}{6} \ (=r)

P(x<y)=1536=512 (=q)P(x<y) = \dfrac{15}{36} = \dfrac{5}{12} \ (=q)

Dl=Xl−Yl=δ1+δ2+⋯+δlD_l = X_l - Y_l = \delta_1 + \delta_2 + \cdots + \delta_l

δ∈{+5, 0, −5}\delta \in \{+5,\ 0,\ -5\}

P(D2=10)=p2=25144P(D_2=10)=p^2=\dfrac{25}{144}

P(D2=5)=2pr=20144,P(D2=0)=r2+2pq=54144P(D_2=5)=2pr=\dfrac{20}{144},\quad P(D_2=0)=r^2+2pq=\dfrac{54}{144}

P(X2≥Y2)=P(D2≥0)=99144=1116 →(Q)P(X_2 \ge Y_2) = P(D_2 \ge 0) = \dfrac{99}{144} = \dfrac{11}{16} \ \to (Q)

P(X2>Y2)=P(D2>0)=45144=516 →(R)P(X_2 > Y_2) = P(D_2 > 0) = \dfrac{45}{144} = \dfrac{5}{16} \ \to (R)

P(D₃=0) = r³ + 6pqr = 8/1728+300/1728

=3081728=77432 →(T)= \dfrac{308}{1728} = \dfrac{77}{432} \ \to (T)

P(D3>0)=P(D3<0)=1−308/17282P(D_3>0) = P(D_3<0) = \dfrac{1 - 308/1728}{2}

=7101728=355864 →(S)= \dfrac{710}{1728} = \dfrac{355}{864} \ \to (S)

I → Q, II → R, III → T, IV → S

Answer: option (1)\boxed{\text{Answer: option (1)}}

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