Show that products of the corresponding terms of sequences a, ar, ar2, .........ar n – 1 and A, AR, AR2, ........ An – 1 form a GP. and find common ratio.
The first term of GP. is 1. The sum of 3rd and 5th term is 90. Find the common ratio of G.P.
Find the sum of the indicated terms of each of the following CP’s:
3, 6, 12, ........; 7 terms
Find the sum to indicated number of terms in each of the geometric progressions:
1, - a, n terms
Prove that the sum to n terms of the series
11 + 103 + 1005 +........ is
Let Sn = 11 + 103 + 1005 + .......... up to n terms
= (10 + 1) + (100 + 3) + (1000 + 5) + ............... upto n terms
= [10 + 100 + 1000 + ..... upto n terms] + [1 + 3 + 5 + .......upto n terms]
= [10 + 102 + 103 + ....... upto n terms] + [ 1 + 3 + 5 +........... upto n terms]
Since the series in the first bracket is a G.P. series with first term 10, common ratio 10 and the
series in the second bracket is an A.P. series with first term 1 and common difference 2.
∴