The $\displaystyle 3^{rd}$ term of a G.P. is $\displaystyle 2/3$ and the $\displaystyle 6^{th}$ term is $\displaystyle 2/81$ then the $\displaystyle 1^{st}$ term is

Find the sum of n terms of the A.P., whose nth term is $\displaystyle 5n + 1$

The sum of first three terms of a G.P. is $\displaystyle \frac{21}{2}$ and their product is 27. Which of the following is not a term of the G.P., if the numbers are positive?

Insert 4 numbers between 2 and 22 such that the resulting sequence is an Arithmetic Progression (A.P.).

Find the sum of series $\displaystyle 1 + \frac{1}{2} + \frac{1}{4} + \dots$ upto 6 terms.

If the sum of '$\displaystyle n$' terms of an AP (Arithmetic Progression) is $\displaystyle 2n^2$, the fifth term is ____.

The sum of first $\displaystyle n$ terms an AP is $\displaystyle 3n^2+5n$. The series is: