If $a_m$ denotes the mth term of an $A.P.$ then $a_m$ =
$\frac{2}{{{a_{m + k}} + {a_{m - k}}}}$
$\frac{{{a_{m + k}} - {a_{m - k}}}}{2}$
$\frac{{{a_{m + k}} + {a_{m - k}}}}{2}$
None of these
Insert five numbers between $8$ and $26$ such that resulting sequence is an $A.P.$
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 $\frac{{{s_n}}}{{{S_{2n}}}}$
In an $A.P.,$ if $p^{\text {th }}$ term is $\frac{1}{q}$ and $q^{\text {th }}$ term is $\frac{1}{p},$ prove that the sum of first $p q$ terms is $\frac{1}{2}(p q+1),$ where $p \neq q$
The number of terms in an $A .P.$ is even ; the sum of the odd terms in it is $24$ and that the even terms is $30$. If the last term exceeds the first term by $10\frac{1}{2}$ , then the number of terms in the $A.P.$ is
The sums of $n$ terms of two arithmetic progressions are in the ratio $5 n+4: 9 n+6 .$ Find the ratio of their $18^{\text {th }}$ terms.