The last banana: A thought experiment in probability – Leonardo Barichello

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In “The Last Banana: A Fun Dive into Probability,” the lesson explores the concept of probability through a game involving two dice to determine who gets the last banana on a deserted island. Despite appearing to have a better chance of winning due to more favorable numbers, the calculations reveal that the friend actually has a higher probability of winning (56% compared to 44%) due to the nature of the possible outcomes when rolling the dice. This lesson highlights how understanding probability can illuminate the randomness inherent in games and real-life scenarios.

The Last Banana: A Fun Dive into Probability

Imagine you and a friend are stuck on a deserted island, and there’s only one banana left. To decide who gets it, you both agree to play a game with two dice. Here are the rules: if the highest number rolled is one, two, three, or four, you win. If it’s five or six, your friend wins. Sounds fair, right? Let’s see!

Rolling the Dice

You roll the dice twice. The first time, you win. The second time, your friend wins. So, who has the better chance of winning overall? At first, it might seem like you have the upper hand because you win with four numbers, while your friend wins with only two. But surprisingly, your friend actually has a better chance of winning each time you roll the dice.

Understanding the Odds

To figure out why, let’s look at all the possible outcomes when you roll two dice. There are 36 different combinations, and each one is equally likely. Even though you have four numbers that can win, the chance of each number being the highest isn’t the same. For example, there’s only a 1 in 36 chance that one will be the highest number, but there’s an 11 in 36 chance that six will be the highest.

Counting the Wins

Out of the 36 possible combinations, you win 16 times, and your friend wins 20 times. This is because you can only win if both dice show a one, two, three, or four. If either die shows a five or six, your friend wins. The chance of one die showing a one, two, three, or four is four out of six.

Calculating Probabilities

Each die roll is independent, meaning one roll doesn’t affect the other. To find the probability of both dice showing a one, two, three, or four, you multiply their probabilities: 4/6 times 4/6, which equals 16/36. Since someone has to win, the chance of your friend winning is 36/36 minus 16/36, or 20/36.

The Nature of Randomness

These calculations show that your friend has a better chance of winning, but it doesn’t mean they will win every time. Dice rolls are random, so even if you play 36 games, you might not win exactly 16 times. However, if you play many games, the results will start to match the probabilities we calculated.

The Final Outcome

So, if you and your friend keep playing this game over and over, your friend will win about 56% of the time, while you’ll win about 44%. But by the time you figure this out, the banana might already be gone!

Understanding probability can be a fun way to see how randomness works in games and in real life. Who knew a simple game with dice could teach us so much?

  1. Reflect on your initial understanding of probability before reading the article. How has your perspective changed after learning about the dice game scenario?
  2. Consider the concept of fairness in games. How does the article challenge or reinforce your ideas about what makes a game fair?
  3. Think about a time when you relied on intuition rather than calculation to make a decision. How might understanding probability have influenced that decision?
  4. Discuss how the concept of randomness, as explained in the article, applies to real-life situations beyond games. Can you think of an example where randomness played a significant role?
  5. How do you feel about the idea that even with a lower probability, you might still win in the short term? How does this affect your approach to risk-taking?
  6. What are some other everyday scenarios where understanding probability might change the way you approach a decision or problem?
  7. Reflect on the importance of understanding mathematical concepts like probability. How can this knowledge impact your personal or professional life?
  8. After reading the article, how do you think you would explain the concept of probability to someone unfamiliar with it, using the dice game as an example?
  1. Dice Probability Experiment

    Grab a pair of dice and a friend. Roll the dice 36 times and record the results. Count how many times you win and how many times your friend wins. Compare your results to the probabilities discussed in the article. Do they match? Discuss why or why not.

  2. Create a Probability Chart

    Draw a chart that shows all 36 possible outcomes of rolling two dice. Highlight the combinations where you win and where your friend wins. Use different colors to make it visually engaging. This will help you visualize why your friend has a better chance of winning.

  3. Probability Storytelling

    Write a short story about a day on the deserted island, incorporating the probability game with the banana. Use creative elements to explain the concept of probability and randomness in a fun and engaging way. Share your story with the class.

  4. Probability Game Design

    Design your own game using dice that involves probability. Create rules and determine the probabilities of different outcomes. Test your game with classmates and discuss how probability affects the game’s fairness and outcomes.

  5. Probability and Real Life

    Research and present how probability is used in real-life situations, such as weather forecasting, sports, or board games. Create a presentation or poster to share your findings with the class, highlighting the importance of understanding probability.

Sure! Here’s a sanitized version of the transcript:

You and a fellow castaway are stranded on a desert island, playing dice for the last banana. You’ve agreed on these rules: You’ll roll two dice, and if the highest number is one, two, three, or four, player one wins. If the highest number is five or six, player two wins.

Let’s try twice more. In the first roll, player one wins, and in the second roll, player two wins. So, who do you want to be? At first glance, it may seem like player one has the advantage since she wins if any one of four numbers is the highest. However, player two actually has an approximately 56% chance of winning each match.

One way to see that is to list all the possible combinations from rolling two dice and count how many each player wins. There are 36 possible combinations, each with the same chance of occurring.

Even though player one has four winning numbers and player two has two, the chance of each number being the highest is not the same. There is only a one in 36 chance that one will be the highest number, but there’s an 11 in 36 chance that six will be the highest.

Out of the 36 possible combinations, 16 give the victory to player one, and 20 give player two the win. You could think about it this way: player one can only win if both dice show a one, two, three, or four. A five or six would mean a win for player two. The chance of one die showing one, two, three, or four is four out of six.

The result of each die roll is independent from the other, and you can calculate the joint probability of independent events by multiplying their probabilities. So, the chance of getting a one, two, three, or four on both dice is 4/6 times 4/6, or 16/36. Since someone has to win, the chance of player two winning is 36/36 minus 16/36, or 20/36.

These probabilities match what we found by making our table. However, this doesn’t guarantee that player two will win, or that if you played 36 games as player two, you’d win 20 of them. That’s why events like dice rolling are considered random.

Even though you can calculate the theoretical probability of each outcome, you might not get the expected results if you examine just a few events. But if you repeat those random events many times, the frequency of a specific outcome, like a player two win, will approach its theoretical probability.

So, if you sat on that desert island playing dice indefinitely, player two would eventually win about 56% of the games, while player one would win about 44%. But by then, of course, the banana would be long gone.

Let me know if you need any further modifications!

ProbabilityThe likelihood or chance of an event happening. – The probability of rolling a three on a standard six-sided dice is 1 out of 6.

DiceA small cube with each side having a different number of dots, used in games to generate random numbers. – When you roll two dice, you can get a total sum ranging from 2 to 12.

OutcomesThe possible results of a probability event. – When flipping a coin, the possible outcomes are heads or tails.

CombinationsDifferent ways of selecting items from a group, where the order does not matter. – The number of combinations for choosing 2 fruits from a basket of 5 is 10.

ChanceThe possibility of a particular outcome occurring. – There is a 50% chance of drawing a red card from a standard deck of cards.

WinningAchieving a desired outcome in a game or probability event. – The winning probability of picking the correct number in a lottery is very low.

RandomWithout a specific pattern, order, or purpose. – The numbers generated by rolling a dice are random.

CalculationsMathematical processes used to determine probabilities or outcomes. – We used calculations to find the probability of drawing an ace from a deck of cards.

GamesActivities involving chance or skill, often used to illustrate probability concepts. – Probability games can help students understand how likely different outcomes are.

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