Hello All ,

i want to solve this geometric series please :

Number of Terms = M

Terms Start From = 1

The Last Term (An) Is 0.5 = 31/16

Find The Number Of Terms "M"

Thanks Sooo Much

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- Oct 12th 2010, 08:12 AMkillersoulsHelp : Find Number Of Terms Of Geometric Series
Hello All ,

i want to solve this geometric series please :

Number of Terms = M

Terms Start From = 1

The Last Term (An) Is 0.5 = 31/16

Find The Number Of Terms "M"

Thanks Sooo Much - Oct 12th 2010, 11:20 AMHallsofIvy
One thing that bothers me about this is you say "The Last Term (An) Is 0.5 = 31/16". Presumably you are aware the 0.5 is NOT equal to 21/16 so that cannot mean what you say. What did you mean by that? Is it possible that the first term is 1, the "common ratio" is 0.5 and the

**sum**of the first M terms is 31/16?

If that is the case then you need to solve $\displaystyle \frac{1- 0.5^{M-1}}{1- 0.5}= 2(1- 0.5^{M-1})= 2- 0.5^M= 31/16.$ for M. - Oct 12th 2010, 12:56 PMkillersouls
NOTE : i've added a picture in this replay so you know what i mean :)

what i mean in (An) = 0.5

is the last term of the series is "grade of last term is" 0.5 "i dont know how but i got it like this " (Surprised)

ya the sum is 31 / 16

and the first term is A1 which is unknown value

but thanks i think your answer was the right one :)

ill come back tomorrow ,,, ill see what's the right answer exactly from my teacher and come back

and thanks again :) - Oct 12th 2010, 12:57 PMkillersouls
but is there any program can solve the series ? ,,, if yes please let me know it's name :)