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    " Find the least value of n such that the sum 3+6+12+24+... to n terms would first exceed 1.5 million"

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    This is my working attached and my answer is slightly different to that of the book's. (The book's answer is my last line of working). The answer I got to was 19.93. Can someone tell me where I went wrong?
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    (Original post by jessyjellytot14)
    Can someone tell me where I went wrong?
    there should be a fullstop after million
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    (Original post by username..1111)
    there should be a fullstop after million
    Will I get the right answer if I put a full stop after million?
    Spoiler:
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    There should be a space between 'full' and 'stop'.
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    it is a GP with a = 3 & r = 2

    Sn = {a ( 1 - r n )} / ( 1 - r ) > 1500000

    put in the values for a, r & find n. you may need logarithms ?
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    (Original post by jessyjellytot14)
    " Find the least value of n such that the sum 3+6+12+24+... to n terms would first exceed 1.5 million"

    Name:  463b23e1-5c85-41a5-a70b-672aecc2567e.jpg
Views: 98
Size:  16.2 KB

    This is my working attached and my answer is slightly different to that of the book's. (The book's answer is my last line of working). The answer I got to was 19.93. Can someone tell me where I went wrong?
    The sum, not the term
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    am I too late?
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    (Original post by TeeEm)
    am I too late?
    yup , i was 22 mins too late ;(
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    (Original post by Naruke)
    The sum, not the term
    (Original post by the bear)
    it is a GP with a = 3 & r = 2

    Sn = {a ( 1 - r n )} / ( 1 - r ) > 1500000

    put in the values for a, r & find n. you may need logarithms ?
    Ohhh okay it makes sense now
 
 
 
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