Q11 of 176 Page 20

The 4th and 7th terms of a G.P. are and respectively. Find the sum of n terms of the G.P.

Nth term of GP is T_n = arⁿ ^{- 1}

⇒ …(1)

Nth term of GP is T_n = arⁿ ^{- 1}

⇒ …(2)

Divide (1) by (2)

⇒

Substituting in 1 we get

a = 1

Sum of GP for n terms =

a = 1, r = , n = n.

⇒

The common ratio of a G.P. is 3, and the last term is 486. If the sum of these terms be 728, find the first term.

The ratio of the sum of the first three terms is to that of the first 6 terms of a G.P. is 125 : 152. Find the common ratio.

Find the sum :

The fifth term of a G.P. is 81 whereas its second term is 24. Find the series and sum of its first eight terms.