Mathematics
Grade 12
15 min
Choose the better bet
Choose the better bet
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1
Introduction & Learning Objectives
Learning Objectives
Model real-world scenarios involving rates and averages using rational functions.
Calculate the expected value of a probabilistic scenario to quantify its long-run outcome.
Analyze the horizontal asymptotes of rational functions to determine long-term trends and limiting values.
Compare two or more rational functions by finding their intersection points and analyzing their behavior.
Apply limits to rational functions to evaluate the behavior of a bet as the number of trials approaches infinity.
Justify a decision between two options by interpreting the mathematical properties of their corresponding rational functions.
Would you rather have a 1/3 chance to win $90 or a 1/10 chance to win $250? 🤔 Let's use rational functions to find the winning strate...
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Key Concepts & Vocabulary
TermDefinitionExample
Rational FunctionA function that can be written as the ratio of two polynomial functions, P(x) and Q(x), in the form f(x) = P(x) / Q(x), where Q(x) ≠0.If a batter has 30 hits in 100 at-bats and then gets x consecutive hits, their new batting average is A(x) = (30 + x) / (100 + x).
Expected Value (E[X])The long-run average outcome of a random event, calculated by summing the products of each possible outcome and its corresponding probability.A coin flip pays $2 for heads (P=0.5) and $0 for tails (P=0.5). The expected value is E[X] = ($2)(0.5) + ($0)(0.5) = $1.
Horizontal AsymptoteA horizontal line y = L that the graph of a function approaches as x approaches ∞ or -∞. In betting scenarios, it represents the long-term average value or success rate.For A(x) = (30 + x) /...
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Core Formulas
Expected Value Formula
E[X] = \sum_{i=1}^{n} x_i P(x_i)
To find the expected value of a bet, multiply each net outcome `x_i` by its probability `P(x_i)` and sum the results. A higher expected value indicates a better bet in the long run.
Long-Run Average (Limit at Infinity)
For f(x) = \frac{ax^n + ...}{bx^m + ...}, \lim_{x \to \infty} f(x) = \begin{cases} a/b & \text{if } n=m \\ 0 & \text{if } n<m \\ \infty \text{ or } -\infty & \text{if } n>m \end{cases}
Use this to find the horizontal asymptote, which represents the limiting average value of a bet or success rate as the number of trials (x) becomes very large.
Comparing Bets
To find when Bet A is better than Bet B, solve the inequality A(x) > B(x).
This helps determine the conditions (e.g., num...
4 more steps in this tutorial
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Challenging
In a repeating game, the cost to play the x-th game is $2. The prize for winning the x-th game is P(x) = (10x+5)/(x+1). The probability of winning any game is a constant 1/4. What is the long-run expected net value per game?
A.$0.50
B.$2.50
C.$2.00
D.$0.00
Challenging
Bet A has an average profit of A(x) = (10x - 20)/x. Bet B has an average profit of B(x) = (kx - 100)/x, where `k` is the prize money. What is the minimum integer value of `k` that makes Bet B the better bet for all x > 20?
A.10
B.13
C.14
D.15
Challenging
Bet A's total profit after x games is a constant P_A(x) = 5x. Bet B's total profit is P_B(x) = (4x²+20x)/(x+1). Bet B is a better choice when its average profit per game is greater than Bet A's. For which interval of games `x` is Bet B the better option?
A.x > 15
B.0 < x < 15
C.x > 5
D.0 < x < 5
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