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Probability question again?

  1. Mar 10, 2013 #1
    I came across this problem in a book that I bought recently. Three dices are dropped. Find the probability that when we roll the dices:

    a) In all the dices we score 5. (Not as a sum) My answer:3/18 = 1/6

    b) In at least one dice we score 6 My answer : 3/18=1/6

    c) The sum of the scores in the dices is smaller or equal to six My answer :
    we have the combinations (1 1 1), (1 1 2), (1 1 3),(1 1 4),(2 1 2), (2 1 3), (4 1 1) so my answer is 7/18

    d) The sum of the scores in the dices is bigger than the product of the scores..I dont know how to do this one

    e) In none of the dices we score 5 or 6.This has to be 3/18+3/18 =6/18=1/3

    f) In two dices we have the same score..I dont know how to do this one either :/
     
  2. jcsd
  3. Mar 10, 2013 #2

    CompuChip

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    Let's start with the first one. Can you explain your answer for a) ?

    How many possible outcomes are there if you throw three dice?
     
  4. Mar 10, 2013 #3

    HallsofIvy

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    By the way- "dice" is itself the plural of the word "die". There is no such word as "dices".
     
  5. Mar 10, 2013 #4

    Ray Vickson

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    It is *very* important that you show us your work, at least for (a) and (b), because I cannot figure out how you could possibly get the types of numbers you have written. Where does the denominator '18' come from?
     
  6. Mar 10, 2013 #5

    CompuChip

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    Ray, I would guess it is 3 * 6, which is an understandable error but incorrect.
     
  7. Mar 10, 2013 #6

    Ray Vickson

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    I knew that, of course, but I wanted the OP to spell it out. No luck so far.
     
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