1per 16+1per 8+1 per 4 +...+16

Un = ar^n-1
16 = 1/16 × 2^n-1
256 (16^2) = 2^n-1
2^8 = 2^n-1
8 = n-1
n = 8 + 1
n = 9
Maka jumlah 9 sukunya
S9 = a (r^n - 1)/ r-1
S9 = 1/16 (2^9 - 1)/ 2-1
S9 = 1/16 (512-1)
S9 = 1/16 (511)
S9 = 511/16

Jawabannya A.