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Math Help - Urgent. i have test tmr.Statistics

  1. #1
    Member helloying's Avatar
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    Urgent. i have test tmr.Statistics

    the qn is in a table format.
    Marks 10 20 30
    no. of pupils 16 10 x

    (a)if the median mark is 20, find the range of x. i am not sure how to do but my ans is 9 to 16. i think i am wrong

    (b)find x if the mean mark is 16. i got x=4
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  2. #2
    Flow Master
    mr fantastic's Avatar
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    Quote Originally Posted by helloying View Post
    the qn is in a table format.
    Marks 10 20 30
    no. of pupils 16 10 x

    (a)if the median mark is 20, find the range of x. i am not sure how to do but my ans is 9 to 16. i think i am wrong Mr F says: If x = 9 the middle value is the 18th (which is 20). If x = 8 the middle values are the 17th and 18th (which is still 20). If x = 16 the middle values are the 21st and 22nd (which is 20). If x = 25 the middle value is the 26th (which is still 20). Therefore the range for x is ......

    (b)find x if the mean mark is 16. i got x=4
    (b) [(16)(10) + (10)(20) + x (30)]/(16 + 10 + x) = 16 => (360 + 30x)/(26 + x) = 16 => x = 4.
    Last edited by mr fantastic; April 1st 2009 at 04:37 AM.
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  3. #3
    Member helloying's Avatar
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    Quote Originally Posted by mr fantastic View Post
    (b) [(16)(10) + (10)(20) + x (30)]/(16 + 10 + x) = 16 => (360 + 30x)/(26 + x) = 16 => x = 16.

    i think u typed wrongly. Isnt x=4 ?
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  4. #4
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    Quote Originally Posted by helloying View Post
    i think u typed wrongly. Isnt x=4 ?
    Yes. I've made the edit.
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