Q&A for How to Calculate Odds

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  • Question
    How do you figure out your odds of winning?
    David Jia
    Academic Tutor
    David Jia is an Academic Tutor and the Founder of LA Math Tutoring, a private tutoring company based in Los Angeles, California. With over 10 years of teaching experience, David works with students of all ages and grades in various subjects, as well as college admissions counseling and test preparation for the SAT, ACT, ISEE, and more. After attaining a perfect 800 math score and a 690 English score on the SAT, David was awarded the Dickinson Scholarship from the University of Miami, where he graduated with a Bachelor’s degree in Business Administration. Additionally, David has worked as an instructor for online videos for textbook companies such as Larson Texts, Big Ideas Learning, and Big Ideas Math.
    Academic Tutor
    Expert Answer
    First, calculate the total number of possible outcomes that you want. For example, if you want to calculate the odds of rolling a 2 on a 6-sided die, that number would be 1, because there's only one side with a 2. Then, figure out how many outcomes you don't want. In this case, that's 5, because there are 5 sides you don't want to roll. In that case, your odds of winning would be 1:5.
  • Question
    What's the difference between odds and probability?
    David Jia
    Academic Tutor
    David Jia is an Academic Tutor and the Founder of LA Math Tutoring, a private tutoring company based in Los Angeles, California. With over 10 years of teaching experience, David works with students of all ages and grades in various subjects, as well as college admissions counseling and test preparation for the SAT, ACT, ISEE, and more. After attaining a perfect 800 math score and a 690 English score on the SAT, David was awarded the Dickinson Scholarship from the University of Miami, where he graduated with a Bachelor’s degree in Business Administration. Additionally, David has worked as an instructor for online videos for textbook companies such as Larson Texts, Big Ideas Learning, and Big Ideas Math.
    Academic Tutor
    Expert Answer
    The odds are the number of outcomes you do want vs the number of outcomes you don't want. If you're trying to roll a certain number on a die, your odds are 1:5. The probability is the number of outcomes you do want divided by the total number of possible outcomes, so with the die, that would be 1/6.
  • Question
    The odds of picking the right box out of two boxes really 50-50?
    Donagan
    Top Answerer
    Yes. There are two possible outcomes and one "right" outcome. One out of two is 50 out of 100, or 50-50.
  • Question
    What is my chance to win once in three draws of a one-in-five chance to win?
    Community Answer
    The chance of winning on a single draw is 20%. Thus, the chance of losing is 80%. The chance of losing all three is .8 x .8 x .8 = .512. Thus, the chance of not losing all three is 1 - .512 = .488. So the probability of winning at least once is 48.8%.
  • Question
    If an event has a probability of 10%, what are the odds in favor of it, and what are the odds against it? Give the odds in simplest form.
    Community Answer
    Nice homework question. Having "a probability of 10%" means that 10% chance of happening every time the event occurs. Therefore, 10% is for it and 90% (100%-10%) is against it. "Percent" broken down and translated means "per 100", so 10% is 10/100 (per=/), or 1/10th.
  • Question
    What are the chances of all ten of ten predictions being accurate?
    Community Answer
    Assuming the event which is being predicted has only 2 outcomes, and is random, and each prediction is one of these 2 outcomes, the chance of all ten predictions being accurate would be 0.5^10.
  • Question
    A total of 198 raffle tickets were sold. One person purchased 5 tickets. What are the odds of one of his tickets being drawn?
    Donagan
    Top Answerer
    It depends on how many tickets are drawn. If only one ticket is drawn, the odds are 5 out of 198, or roughly 1 in 40.
  • Question
    What are the better odds in horse racing: 3/1 or 5/2?
    Community Answer
    5/2 odds are the same as 2.5/1 odds. Now, it depends on what you mean by "better". 3/1 odds means an extra $0.50 profit per dollar wagered, if you win. 5/2 odds pays less when you win, but you should expect to win more often.
  • Question
    I have 120 entries I can use across 4 raffles. Are my chances better using them all on 1 raffle or dividing them across all 4?
    Community Answer
    Of course this depends on how many entries others have, but I would go with spreading them out evenly across 3 or all 4.
  • Question
    If I have a 1 in 5,000 chance of winning on a given day, and I play every day, how many times am I likely to win in a year?
    Community Answer
    You are not likely to win in a year. The odds of winning are 365/5000. If you divide 5000 by 365 (days in a year) you get 13.698, so it should take over 13 years for you to win.
  • Question
    What are the odds of getting heads 12 times in a row?
    Community Answer
    Every time you toss an unbiased coin, it's always a 50/50 chance. If the coin lands on heads 11 times, the odds are still 50/50 on the twelfth.
  • Question
    How many people do I need to ask to find two people with the same birthday?
    Donagan
    Top Answerer
    Considering that February 29 is a possible birthday (so that a year could have 366 dates), you might have to interview as many as 367 people to find a match.
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