How many terms of the series 2 + 6 + 18 + …. Must be taken to make the sum equal to 728?


Given:


Sum of GP = 728


∴ Common Ratio = r =


a = 2


To find: Number of terms = n.


Sum of GP for n terms =


⇒


⇒ 728 = 3n - 1


⇒ 729 = 3n


⇒ 36 = 3n


∴ n = 6.


6
1