The first term of a GP is 27, and its 8th term is . Find the sum of its first 10 terms.
‘Tn’ represents the nth term of a G.P. series.
Tn = arn-1
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⇒
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⇒
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∴
Sum of a G.P. series is represented by the formula, , when |r|<1. ‘Sn’ represents the sum of the G.P. series upto nth 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
∴
⇒
⇒
⇒
∴