Sigma Percentile
JEE Advanced 2016
LEVELJEE Main

Animated Solution for Mathematics - Probability: Comprehension Passage

Football teams and have to play two games against each other. It is assumed that the outcomes of the two games are independent. The probabilities of winning, drawing and losing a game against are 1/2, 1/6 and 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 and denote the total points scored by teams and respectively after two games.
Question 1:

is

Select Answer:

Question 2:

is

Select Answer:

Visualized Solution

Defining Probabilities

  • Probabilities for Team in a single game:
  • Win: (3 points)
  • Draw: (1 point)
  • Loss: (0 points)

The Sample Space

  • Total outcomes =
  • Since games are independent:
  • We represent outcomes as pairs: where is points, is points.

Analyzing : Case

  • Condition: (Team scores more points)
  • Case 1: (Win Game 1, Win Game 2)
  • Points: ,
  • Probability:

Analyzing : Cases and

  • Case 2: One Win, One Draw ( or )
  • Points: ,
  • Probability:
  • Probability:

Total Probability

  • Total
  • Substitute values:
  • Simplify:
  • Final Result:

Analyzing : Cases and

  • Condition: (Both teams score equal points)
  • Case 1: One Win, One Loss ( or )
  • Points: ,
  • Probability:
  • Probability:

Analyzing : Case

  • Case 2: Two Draws ()
  • Points: ,
  • Probability:

Total Probability

  • Total
  • Substitute values:
  • Simplify:
  • Final Result:

The Sigma Insight: Addition and Multiplication Theorems

Solution Diagram

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, and , battle it out over two intense games.
Our goal is to predict the outcome of their total points, and . 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 : a win () with , a draw () with , and a loss () with .
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 grid of possibilities. There are total outcomes.

The Quest for

The first challenge is to find the probability that scores more points than . We need to hunt for the scenarios where .
The most dominant scenario is (Win-Win). Here, earns points, while earns points. The probability is:
Consider (Win-Draw) and (Draw-Win). In both cases, earns points, and earns point. Since , these are valid.
The probability for is , and for it is . Adding these up, we get:

The Equilibrium of

Now, the second challenge: when do the teams tie? We need .
One path is (Win-Loss) or (Loss-Win). In both, gets points and gets points. The probability for is , and for it is .
What about (Draw-Draw)? Here, gets points and gets points. This is a valid tie with probability:
Summing these, we get:

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!

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