Tentukan jumlah suku ke 5 dari deret 600 + 300 + 150 ....

U1= 600
U2= 300
Rasio = U2/U1 = 1/2

S5 = u1 ( 1 - r^5) / ( 1-r)
= 600 (1- 1/2^5 ) / ( 1- 1/2)
= 600 ( 1- 1/32) / 1/2
= 600 ( 32-1) /32 x 2/1
=600 ×31 /32×2
= 1200 × 31/32
=1.162,5