Find the $12^{th}$ term of the $A.P.$ $9, 13, 17, 21, \ldots$

$A$ person saved $Rs. 16,500$ in all during $10$ years. After the first year,every year he saved $Rs. 100$ more than what he had saved the previous year. Find his savings of the first year.

For the $A.P.$ $3, 13, 23, 33, \ldots,$ its $\ldots \ldots \ldots \ldots$ term exceeds its $21^{st}$ term by $10.$

Find the sum of all the $11$ terms of an $AP$ whose middle most term is $30$.

The sum of how many terms of the $A.P.$ $9, 17, 25, \ldots$ is $636$?

For an $A.P.$,the first term is $5$ and the common difference is $3$. Then,the $15^{th}$ term of the $A.P.$ is..........