Chapter 24: Problem 104
A bag contains \(a\) white and \(b\) black balls. Two players \(A\) and \(B\) alternately draw a ball from the bag, replacing the ball each time after the draw till one of them draws a white ball and and wins the game. If \(A\) begins the game and the probability of \(A\) winning the game is three times that of \(B\), then \(a: b=\) (A) \(2: 1\) (B) \(3: 1\) (C) \(3: 2\) (D) none of these
Short Answer
Step by step solution
Identify Variables and Probabilities
Write the Expression for A Winning
Solve for A's Probability
Write the Expression for B Winning
Set Up Relationship Between A's and B's Probability
Simplify the Equation and Solve for a:b
Match Final Ratio to Answer Choices
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Ratio
In the exercise given, we identify that the probability of drawing a white ball relative to all balls in the bag is central. The ratio of white balls \( a \) to black balls \( b \), \( a:b \), is essential. It's not just about counting; it's about relation.
- Ratios simplify comparisons between two quantities.
- A ratio of \( 3:2 \), for instance, means for every 3 white balls, there are 2 black balls.
Probability Theory
Probability provides a way to measure the likelihood of events using simple calculations. Here, the probability of player A winning, \( P_A \), and player B winning, \( P_B \), were calculated using probabilities of drawing specific ball colors:
- \( P(W) = \frac{a}{a+b} \): Probability of drawing a white ball
- \( P(B) = \frac{b}{a+b} \): Probability of drawing a black ball
Combinatorics
In this exercise, combinatorics helps in calculating the various outcomes possible when players draw balls in turns. The combinations of sequences where player A or player B could draw balls until one wins are vast.
By employing combinatorial methods, we can figure out the probability dependencies, like if one must draw a series of black balls before drawing a white ball. Though often complex, combinatorics make these analyses feasible by breaking them into smaller, manageable calculations:
- Counting paths of sequences in drawing balls
- Breaking down multi-step probabilities