SOLUTION: t is an even number in the series 1/t + 3/t + 5/t +.......+ t-1/t (1) Determine the number of terms in the series in terms of t. (Determine the sum of the series in terms of

Algebra ->  Sequences-and-series -> SOLUTION: t is an even number in the series 1/t + 3/t + 5/t +.......+ t-1/t (1) Determine the number of terms in the series in terms of t. (Determine the sum of the series in terms of       Log On


   



Question 1140702: t is an even number in the series 1/t + 3/t + 5/t +.......+ t-1/t
(1) Determine the number of terms in the series in terms of t.
(Determine the sum of the series in terms of t.
(3) Hence or otherwise evaluate :
(1/4 + 3/4) + (1/6 + 3/6 + 5/6) + (1/8 + 3/8 + 5/8 +7/8)+.....+ (1/50 + 3/50 + 5/50)+....+(49/50)
Can I get help please

Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


The series is arithmetic, with a common difference of 2/t.

(1) To find the number of terms in an arithmetic series...
find the difference between the last and first terms;
divide by the common difference; and
add 1.

%28t-1%29%2Ft-1%2Ft+=+%28t-2%29%2Ft
%28%28t-2%29%2Ft%29%2F%281%2Ft%29+=+t-2
%28t-2%29%2F2+=+t%2F2-1
%28t%2F2-1%29%2B1+=+t%2F2

ANSWER (1): The number of terms in the series is t/2.

(2) The sum of the terms of any series is the number of terms, multiplied by the average of all the terms; since this sequence is arithmetic, that means the sum is the number of terms, multiplied by the average of the first and last terms.

%28t%2F2%29%2A%28%281%2Ft%29%2B%28t-1%29%2Ft%29%2F2
%28t%2F2%29%2A%28%28t%2Ft%29%2F2%29
%28t%2F2%29%2A%281%2F2%29+=+t%2F4

ANSWER: (2): The sum of the terms in the series is t/4.

(3) The terms in this series are all of the form in the above discussion. The values of t in the terms of this series are 4, 6, 8, ..., and 50. So the sum of this series, using the result in (2), is

4%2F4%2B6%2F4%2B8%2F4 ... + 50%2F4

This is again an arithmetic series; the sum is number of terms, multiplied by the average of the first and last:

24%28%284%2F4%2B50%2F4%29%2F2%29+=+24%2854%2F8%29+=+54%2A3+=+162