Q1 of 176 Page 20

Find the sum of the following geometric progressions :

1, 3, 9, 27, … to 8 terms

Common Ratio = r =


∴ Sum of GP for n terms = …(1)


⇒ a = 1, r = 3, n = 8


∴ Substituting the above values in (1) we get


⇒


⇒ (38 – 1)/2


⇒ 3280


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