The nth term of a G.P. is 128 and the sum of its n terms is 255. If its common ratio is 2, then find its first term.

Given, a n = 128, r = 2 and S n = 255. By formula a n = ar n - 1 ∴ 128 = a(2) n - 1 By formula, Putting value of 2 n from Eq 1 in above Equation, Hence, the first term of the G.P. is 1.