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Probability Store Problem

  1. Oct 13, 2006 #1
    Hi i need help on the following question:

    In a teashop 70% of customers order tea with milk, 20% tea with lemon and 10% with neither. of those taking tea with milk 3/5 take sugar, of those taking tea with lemon 1/4 take sugar, and of those taking tea with neither milk or lemon 11/20 take sugar. a customer is then chosem at random.

    i need to find the probability that the customers take suggar or milk or both. i know that the answer is o.525 but i dont know how.

    can anybody help me please???
  2. jcsd
  3. Oct 13, 2006 #2


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    Hint: the word 'or' is interpreted as the operation '+' while calculating probabilities.
  4. Oct 13, 2006 #3
    yes i understand that
    but does that mean that i do

    (0.7x3/5) + 0.7 + 3/5 + 1/4 + 11/20
    if this is the case then it doesnt equal 0.525
  5. Oct 13, 2006 #4


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    Not only it doesn't equal 0.525 , but it is greater than 1, which cannot be. Just to make sure, the question is: 'Calculate the probability that the person chosen takes (sugar OR milk) OR (sugar AND milk)'? The case (sugar OR milk) would not make sence, because every one is taking sugar.
  6. Oct 13, 2006 #5
    i cant really make sense of the question either, but i think it means (sugar and milk) or (sugar or milk)
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