The 8^th term of a G.P. is 192 and its common ratio is 2, then the first term of the G.P. is :

1. 3

2. $\dfrac{1}{3}$

3. $\dfrac{2}{3}$

4. $\dfrac{3}{2}$

Let first term of G.P. be a and common ratio be r.

By formula,

⇒ a_n = ar^{n - 1}

Given,

8^th term of a G.P. is 192.

⇒ a₈ = 192

⇒ ar^{8 - 1} = 192

⇒ ar⁷ = 192

Substituting value of common ratio (r) = 2 in above equation, we get :

⇒ a(2)⁷ = 192

⇒ 128a = 192

⇒ a = $\dfrac{192}{128} = \dfrac{3}{2}$.

Hence, Option 4 is the correct option.