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Math Help - Probability

  1. #1
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    Probability

    I put ten balls into a box, each ball has a number on it, from 1 to 10.
    I will draw 6 times, once i draw a ball, I will not put the ball back into the box.

    1. What is the probability that I will draw a number 2 OR a number 3 ball?

    2. What is the probability that I will draw a number 2 AND a number 3 ball?
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  2. #2
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    Quote Originally Posted by cammywhite View Post
    I put ten balls into a box, each ball has a number on it, from 1 to 10.
    I will draw 6 times, once i draw a ball, I will not put the ball back into the box.

    1. What is the probability that I will draw a number 2 OR a number 3 ball?
    The first time you draw, there are 10 balls, 8 of which are NOT 2 or 3. The probability you will not draw 2 or 3 is 8/10. Assuming you did not draw a 2 or 3, there are now 9 balls left 7 of which are not 2 or 3. The probabilty you do not draw 2 or 3 is now 7/9. Then there are 8 balls, 6 of which are not 2 or 3- probability of drawing 2 or 3 is 6/8... It should become clear that the probability of not drawing a 2 or 3 in 6 draws is
    \frac{8}{10}\frac{7}{9}\frac{6}{8}\frac{5}{7}\frac  {4}{6}\frac{3}{6}.

    2. What is the probability that I will draw a number 2 AND a number 3 ball?
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