If $a, b, c$ are in Arithmetic Progression,then $(a - c)^2 = \dots$

The interior angles of a polygon with $n$ sides are in an $A.P.$ with a common difference of $6^{\circ}$. If the largest interior angle of the polygon is $219^{\circ}$,then $n$ is equal to . . . . . .

Let the sequence $a_1, a_2, a_3, \dots, a_{2n}$ form an $A.P.$ Then $a_1^2 - a_2^2 + a_3^2 - a_4^2 + \dots + a_{2n - 1}^2 - a_{2n}^2 = $

What is the sum of all integers between $81$ and $719$ that are divisible by $5$?

If for an arithmetic progression $S_{2n} = 2S_n$,then $S_{3n} / S_n = \dots$

The sum of $n$ arithmetic means between $a$ and $b$ is: