The arithmetic mean of first $n$ natural number
$\frac{{n - 1}}{2}$
$\frac{{n + 1}}{2}$
$\frac{n}{2}$
$n$
If $b + c,$ $c + a,$ $a + b$ are in $H.P.$, then $\frac{a}{{b + c}},\frac{b}{{c + a}},\frac{c}{{a + b}}$ are in
The sum of the common terms of the following three arithmetic progressions.
$3,7,11,15,...................,399$
$2,5,8,11,............,359$ and
$2,7,12,17,...........,197$, is equal to $................$.
If $a_m$ denotes the mth term of an $A.P.$ then $a_m$ =
A man deposited $Rs$ $10000$ in a bank at the rate of $5 \%$ simple interest annually. Find the amount in $15^{\text {th }}$ year since he deposited the amount and also calculate the total amount after $20$ years.
Three number are in $A.P.$ such that their sum is $18$ and sum of their squares is $158$. The greatest number among them is