Given: G.P.

We know that in G.P a_n = ar^n-1

Here, n: number of terms

a: First term = 5/2

r: common ratio

Common ratio of the given G.P is: (∴ r = 1/2)

Here, n^th team of the G.P :

∴ n^th term of the given G.P. is

20^th term of the given G.P. is

∴ n^th and 20^th term of the given G.P. are: respectively.