Let $a_n, n \geq 1$, be an arithmetic progression with first term $2$ and common difference $4$ . Let $M_n$ be the average of the first $n$ terms. Then the sum $\sum \limits_{n=1}^{10} M_n$ is
$110$
$335$
$770$
$1100$
If $19^{th}$ terms of non -zero $A.P.$ is zero, then its ($49^{th}$ term) : ($29^{th}$ term) is
Let $S_n$ and $s_n$ deontes the sum of first $n$ terms of two different $A.P$. for which $\frac{{{s_n}}}{{{S_n}}} = \frac{{3n - 13}}{{7n + 13}}$ then $\frac{{{s_n}}}{{{S_{2n}}}}$
The number of terms in the series $101 + 99 + 97 + ..... + 47$ is
Find the sum of all numbers between $200$ and $400$ which are divisible by $7.$
Write the first three terms in each of the following sequences defined by the following:
$a_{n}=2 n+5$