The first term of a GP is 27, and its 8^th term is . Find the sum of its first 10 terms.

‘T_n’ represents the n^th term of a G.P. series.

T_n = ar^n-1

⇒

⇒

⇒

⇒

⇒

∴

Sum of a G.P. series is represented by the formula, , when |r|<1. ‘S_n’ represents the sum of the G.P. series upto n^th terms, ‘a’ represents the first term, ‘r’ represents the common ratio and ‘n’ represents the number of terms.

Here,

a = 27

r = (ratio between the n term and n-1 term)

n = 10 terms

∴

⇒

⇒

⇒

∴