Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Need help with probability question

  1. Dec 6, 2004 #1
    I don't know how to do this probability question:

    A roulette wheel consists of 38 numbers: 1 to 36, 0, and 00. What is the probability that a roulette ball will come to rest on an even number other than 0 or 00?

    My textbook says the answer is 9/19 but I don't know how they got that. Please help!!!
  2. jcsd
  3. Dec 6, 2004 #2
    There are 18 even numbers between 1-36. Add two to your denominator and then you have an 18/38 chance of getting an even number that isn't 0 or 00. Reduce your fraction by dividing by two.

  4. Dec 6, 2004 #3
    The probability in this case just consists of counting the number of outcomes you're interested in versus all possible outcomes. How many even numbers are there on the roulette wheel ? How many numbers in total ?
  5. Dec 6, 2004 #4


    User Avatar
    Science Advisor
    Homework Helper

    You should be knowing that probability is basically the number of favorable cases devided by the number of all possible cases.
    The number of possible cases is obviously 38,because all 38 numbers have a chance of showing up,and moreover,this chance is equal,since they are all distinct.
    The number of favorable cases is the number of even numbers in the list excluding 0 and 00.I'll let u think about it.Once u got this number right,plunge it,together with 38,in the definition of probability and i'm pretty sure you'll get 9/19.

    Last edited: Dec 6, 2004
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook