Question

Find the sum of ten terms of the G. P 1,1.3,1.69​

Answer 1

Sum of G.P. series is given by,

Sum=

r−1

a(r

n

−1)

when r>1

Where a= first term, n=n

th

term and r is common ratio.

Here, a=1,n=10,r=

3

S

10

=

(

3

−1)

1×{(

3

)

10

−1}

=

(

3

−1)

(3

5

−1)

×

(

3

+1)

(

3

+1)

=

(3−1)

242(

3

+1)

=121(

3

+1).