The answer is:
Sigma 960 (1/4)^i-1 ; the sum is 1280
We are given the first term of the geometric sequence as:
[tex]a_1=960[/tex]
Also, the common ratio of the terms in geometric sequence is: [tex]\dfrac{1}{4}[/tex]
We know that if the series is a geometric series than the sum of the terms is given by:
[tex]a+ar+ar^2+.....\\\\=a(1+r+r^2+....)\\\\=\sum ar^{n-1}[/tex]
where a is the first term of the series and r is the common difference.
Here a=960
and r=1/4
Hence,
The sum of the series is:
[tex]=\sum 960(\dfrac{1}{4})^{i-1}[/tex]
Now we know that the sum of the infinite geometric series is given by:
[tex]S=\dfrac{a}{1-r}[/tex]
where S is the sum of the series.
Hence, here the sum of the series is calculated by:
[tex]S=\dfrac{960}{1-\dfrac{1}{4}}\\\\\\S=\dfrac{960}{\dfrac{3}{4}}\\\\\\S=\dfrac{960\times 4}{3}\\\\\\S=1280[/tex]
Hence, the sum is: 1280
