The sum of $n$ arithmetic means between $a$ and $b$, is
$\frac{{n(a + b)}}{2}$
$n(a + b)$
$\frac{{(n + 1)(a + b)}}{2}$
$(n + 1)(a + b)$
The number of $5 -$tuples $(a, b, c, d, e)$ of positive integers such that
$I.$ $a, b, c, d, e$ are the measures of angles of a convex pentagon in degrees
$II$. $a \leq b \leq c \leq d \leq e$
$III.$ $a, b, c, d, e$ are in arithmetic progression is
The sum of the integers from $1$ to $100$ which are not divisible by $3$ or $5$ is
Find the sum of all numbers between $200$ and $400$ which are divisible by $7.$
Find the sum to $n$ terms of the $A.P.,$ whose $k^{\text {th }}$ term is $5 k+1$
If $a,b,c$ are in $A.P.$, then $\frac{1}{{\sqrt a + \sqrt b }},\,\frac{1}{{\sqrt a + \sqrt c }},$ $\frac{1}{{\sqrt b + \sqrt c }}$ are in