If the sum of $n$ terms of an $A.P.$ is $2n^2 + 5n$,then the $n^{th}$ term will be

$A$ software company sets up $m$ number of computer systems to finish an assignment in $17$ days. If $4$ computer systems crashed on the start of the second day,$4$ more computer systems crashed on the start of the third day and so on,then it took $8$ more days to finish the assignment. The value of $m$ is equal to :

The sums of $n$ terms of two arithmetic progressions are in the ratio $5n+4 : 9n+6$. Find the ratio of their $18^{th}$ terms.

If the $9^{th}$ and $19^{th}$ terms of an arithmetic progression are $35$ and $75$ respectively,what is its $20^{th}$ term?

The sum of all two-digit numbers which,when divided by $4$,yield unity as a remainder is:

There are $15$ terms in an arithmetic progression. Its first term is $5$ and their sum is $390$. The middle term is