# Thread: Sum of finite series

1. ## 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.

Thanks

You can first use 17! as denominator. You can then find that it is a very standard AP and GP questions.

Originally Posted by champrock
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.

Thanks

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

and the answer cannot be 1. There is no such option

4. Originally Posted by Schung
The answer is not quite exactly equal to 1. To paraphrase the greatest spy of all time - Missed it by this much: $\frac{2}{10854718875}$ ....