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Math Help - Sum of finite series

  1. #1
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    Sum of finite series

    What is the value of

    1*2 / 3! + (2*2^2)/4! + (3*2^3)/5! ............... (15*2^15)/17!

    I tried making a general term for this but was unable to proceed further with that method. Secondly I multiplied the sum by 2 and tried to subtract it from the original (AP-GP sort of a method) but that is also not taking me any further.

    Please guide me on this.

    Thanks
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  2. #2
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    The answer is 1.
    You can first use 17! as denominator. You can then find that it is a very standard AP and GP questions.


    Quote Originally Posted by champrock View Post
    What is the value of

    1*2 / 3! + (2*2^2)/4! + (3*2^3)/5! ............... (15*2^15)/17!

    I tried making a general term for this but was unable to proceed further with that method. Secondly I multiplied the sum by 2 and tried to subtract it from the original (AP-GP sort of a method) but that is also not taking me any further.

    Please guide me on this.

    Thanks
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  3. #3
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    didnt quite get how u are taking 17! as denominator?

    and the answer cannot be 1. There is no such option
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  4. #4
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    Quote Originally Posted by Schung View Post
    The answer is 1.
    You can first use 17! as denominator. You can then find that it is a very standard AP and GP questions.
    The answer is not quite exactly equal to 1. To paraphrase the greatest spy of all time - Missed it by this much: \frac{2}{10854718875} ....
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  5. #5
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    hehe.. actually the options given are all pretty close. so , there is no way to figuring out that ways.

    the correct answer is given as 1- (2^16)/17!

    any way to derive this?
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