Question

I don't understand Geometric series and this problem.
Evaluate S_5 for 600+300+150+....
Choices
1,162.5
581.25
18600
37.5
I got the wrong answer twice and it's not 37.5
Please help...

Answer 1

so than you see first term is
1. 600 and
2. 600/2 = 300 than
3.300/2=150
4.150/2=75
5. 75/2=37,5

this is clearly now ?

Answer 2

a1=600
a2= 300
a3 = 150

common ratio (r) = a3/a2
= 150/300
= 1/2 [ r is less than 1]

sn = a {r^n -1]/(r-1) [ here a= a1= 600, r= 1/2 , n= 5]


find
s5=