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Thread: Math-problem

  1. #1 Math-problem 
    Forum Masters Degree thyristor's Avatar
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    Here's an easy problem. See if you can solve it!
    A man asks his neighbour how old her three daughters are. She says that the product of their ages is 36 and that the sum of them is the man's number on his house.
    The man says he needs more information and his neighbour then says that her eldest daughter plays football.
    How old are her daughters?


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  3. #2  
    Forum Professor sunshinewarrior's Avatar
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    Unless girls are banned from football before the age of 7 you have two options:

    1. Twins of 2 and an older sister of 9 (Sum = 13)

    2. Girls of 2 and 3 and an older of 6 (Sum = 11)

    On balance I'd go for option 2 on the grounds that enough people are superstitious enough not to have the number 13 as their house number...


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  4. #3  
    Forum Masters Degree thyristor's Avatar
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    Nice point, but unfortunately wrong.
    The three girls can be of the ages 1,1,36 1,2,18 1,3,12 1,4,9 1,6,6
    2,2,9 2,3,6.
    The sum of these ages are 38,21,16,14,13,13 and 11.
    Since the man knows his own house number he to be able to know their age know but there are two with the sum 13. When his neighbour then says that her eldest daughter plays football he knows that she can't have two girls of the same age that are older than the last one and therefore it must be 2,2,9.
    373 13231-mbm-13231 373
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  5. #4  
    Forum Professor sunshinewarrior's Avatar
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    Quote Originally Posted by thyristor
    Nice point, but unfortunately wrong.
    The three girls can be of the ages 1,1,36 1,2,18 1,3,12 1,4,9 1,6,6
    2,2,9 2,3,6.
    The sum of these ages are 38,21,16,14,13,13 and 11.
    Since the man knows his own house number he to be able to know their age know but there are two with the sum 13. When his neighbour then says that her eldest daughter plays football he knows that she can't have two girls of the same age that are older than the last one and therefore it must be 2,2,9.
    Cool!
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  6. #5  
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    One of the twins is a little older than the other.
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  7. #6  
    Forum Masters Degree thyristor's Avatar
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    What do you mean?
    373 13231-mbm-13231 373
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  8. #7  
    Forum Professor serpicojr's Avatar
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    Harold's saying, in any pair of twins, one is older. So this woman could be talking about an older twin when saying the oldest one plays soccer.
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