That finite sequence we can just add up, using 16 as a common denominator
[tex]1 + 1/2 + 1/4 + 1/8+1/16 = 16/16 + 8/16 + 4/16+2/16+1/16 = (16+8+4+2+1)/16=31/16[/tex]
They probably want you to use the formula
[tex]S_n = \sum_{k=0}^{n-1} r^k = \dfrac{1 - r^n}{1-r}[/tex]
That's the special case of a geometric series where the first term is one. If it's not we multiply the answer by the first term.
In our example, r=1/2 and n=5, meaning five terms.
[tex]S_5 = \dfrac{ 1- (1/2)^5}{1- (1/2)} = \dfrac{1-1/32}{1/2}=\dfrac{31/32}{1/2}=\dfrac{31}{15}[/tex]
Same answer, math works!
If the question was asking about the infinite geometric series, that's just a little bigger:
[tex]S = \dfrac{1}{1-r} = \dfrac{1}{1 - \frac 1 2} = 2[/tex]
