I'm guessing we have
S1 = 1000
S2 = 1000 + 500
S3 = 1000 + 500 + 250
S4 = 1000 + 500 + 250 + 125
S5 = 1000 + 500 + 250 + 125 + 62.5
Just adding that up, S5 is
Answer: 1937.5
Do they want you to use the geometric series formula? We'll check it that way.
We have first term a=1000 and common ratio r=1/2. In general
[tex]S_n = \dfrac{a(1 - r^n)}{1-r}[/tex]
For us that's
S5 = (1000 (1 - (1/2)^5))/(1 - 1/2) = 2000(1 - 1/32)
= 2000(31)/32 = 62000/32 = 1937.5 √
Math works!
