Analyzing the Setup
Welcome, future engineer! Today, we are not just solving a probability problem; we are stepping into the shoes of a football analyst. Imagine you are standing on the sidelines, watching two teams, T1 and T2, battle it out over two intense games.
Our goal is to predict the outcome of their total points, X and Y. Probability is often intimidating because it feels like guessing, but in the JEE Advanced arena, it is actually about systematic counting.
First, we must respect the individual game. We are given the probabilities for T1: a win (W) with P(W)=21, a draw (D) with P(D)=61, and a loss (L) with P(L)=31.
Since the two games are independent, the probability of any sequence of two games is simply the product of their individual probabilities. Think of this as a 3×3 grid of possibilities. There are 3×3=9 total outcomes.
The Quest for X>Y
The first challenge is to find the probability that T1 scores more points than T2. We need to hunt for the scenarios where X>Y.
The most dominant scenario is WW (Win-Win). Here, T1 earns 3+3=6 points, while T2 earns 0+0=0 points. The probability is:
Consider WD (Win-Draw) and DW (Draw-Win). In both cases, T1 earns 3+1=4 points, and T2 earns 0+1=1 point. Since 4>1, these are valid.
The probability for WD is 21×61=121, and for DW it is 61×21=121. Adding these up, we get:
P(X>Y)=41+121+121=123+122=125
The Equilibrium of X=Y
Now, the second challenge: when do the teams tie? We need X=Y.
One path is WL (Win-Loss) or LW (Loss-Win). In both, T1 gets 3+0=3 points and T2 gets 0+3=3 points. The probability for WL is 21×31=61, and for LW it is 31×21=61.
What about DD (Draw-Draw)? Here, T1 gets 1+1=2 points and T2 gets 1+1=2 points. This is a valid tie with probability:
Summing these, we get:
P(X=Y)=61+61+361=31+361=3612+361=3613
Final Takeaway
The math is not just about numbers; it is about accounting for every single possibility without bias. By breaking the problem into independent events and summing the mutually exclusive cases, we turned a complex scenario into a simple, logical flow.
Keep this systematic approach in your toolkit, and no probability problem will ever intimidate you again. Keep pushing, keep learning!