The sum of n terms of a G.P. with first term a and common ratio r, when r < 1, is :

1. $\dfrac{ar^n-1}{r-1}$

2. $\dfrac{1-ar^n}{1-r}$

3. $\dfrac{a(r^n-1)}{r-1}$

4. $\dfrac{a(1-r^n)}{1-r}$

The general term of the G.P. $\dfrac{1}{4}, -\dfrac{1}{2}, 1, -2, 4, \dots$ is :

1. (-1)^{(n - 1)} × 2^{(n - 3)}

2. (-1)^{(n - 1)} × 2^{(n - 2)}

3. (-1)^{(n - 1)} × (-2)^{(n - 1)}

4. (-1)^{(n - 1)} × (-2)^{(n - 3)}

Which term of the G.P. $\sqrt{3}, 3\sqrt{3}, 9\sqrt{3}, \dots$ is $729\sqrt{3}$ ?

1. 7th

2. 6th

3. 9th

4. 8th

If a₁, a₂, a₃, ……., a_n is a G.P. having common ratio r and k is a natural number such that 3 < k < n, then r is equal to :

1. $\dfrac{a$k}{a{1}}

2. $\dfrac{a$1}{a2}

3. $\dfrac{a$k}{a{n-3}}

4. $\dfrac{a${k-1}}{a{k-2}}