no. 35 tolong dong cepat ya

a = 5 cm
S4 = ar^3 = 135
n = 4

ar^3 = 135
5r^3 = 135
r^3 = 135/5
r^3 = 27
r^3 = 3^3
r = 3

Dn = a(1 - r^n)/1 - r
D4 = 5(1 - 3^4)/1 - 3
D4 = 5(1 - 81)/-2
D4 = 5(-80)/-2
D4 = -400/-2
D4 = 200

Jadi panjang tali semula adalah 200 cm