Question

Find the sum of the first 7 terms of the following series 10,4,8/5

Answer 1

16.6

Explanation:

Since the numbers are decreasing as multiples, its a geometric progression.

`S_(n)=(a(1-r^(n) ))/(1-r) ; r\\eq 1 \ and\ r \ is\ less\ than\ 1\\common\ ratio=(4)/(10)=(2)/(5)\\ S_(7)=(10(1-(2/5)^(7) ))/(1-(2/5)) \\=16.6`