tentukan jumlah setiap deret geometri jika 16+8+4+2 sampai 11 suku

a = 16
r = 1/2
S11....?

jawab : 

Sn = a(1 - r^n)/ 1 - r
S11 = 16 (1 - 1/2^11) / 1 - 1/2
S11 = 16 (1 - 1/2048) / 1/2
S11 = 16 (2048 - 1)/2048 x 2
S11 = 32 (2047) / 2048
S11 = 2047/64

maaf kalau salah