The sum of three numbers in a geometric progression is $\displaystyle 28$. When $\displaystyle 7$, $\displaystyle 2$ and $\displaystyle 1$ are subtracted from the first, second and the third numbers respectively, then the resulting numbers are in arithmetic progression. What is the sum of squares of the original three numbers?

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: