JEE Advanced · Mathematics · 32. Probability

Paragraph:

Football teams $T_{1}$ and $T_{2}$ have to play two games against each other. It is assumed that the outcomes of the two games are independent. The probabilities of $T_{1}$ winning, drawing and losing a game against $T_{2}$ are $\frac{1}{2}, \frac{1}{6}$ and $\frac{1}{3}$, respectively. Each team gets $3$ points for a win, $1$ point for a draw and $0$ point for a loss in a game. Let $X$ and $Y$ denote the total points scored by teams $T_{1}$ and $T_{2}$, respectively, after two games.

Question:

$P(X>Y)$ is

A $\frac{1}{4}$
B $\frac{5}{12}$
C $\frac{1}{2}$
D $\frac{7}{12}$

Verified Solution

Answer & Solution

Correct Answer

(B) $\frac{5}{12}$

Step-by-step Solution

Detailed explanation

P (X > Y) = P (T_{1} w i n) P (T_{1} w i n) + P (T_{1} w i n) P (m a t c h d r a w) + P (m a t c h d r a w) . P (T_{1} w i n)

= \frac{1}{2} \times \frac{1}{2} + \frac{1}{2} \times \frac{1}{6} + \frac{1}{6} \times \frac{1}{2} = \frac{5}{12}

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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