Question

Find the sum of the first 10 terms 125,50,20

Answer 1

208.3

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=(20)/(50)=(2)/(5)\\ S_(10)=(125(1-(2/5)^(10) ))/(1-(2/5)) \\=208.3`