The $n^{th}$ term of an $A.P.$ is denoted by:

For the finite $A.P.$ $1, 4, 7, \ldots, 118,$ find the $15^{th}$ term from the end.

In each of the following,$a$ and $d$ for an $A.P.$ are given. Find the $A.P.$ in each case. $a = 21, d = -7$.

The sum of the first $n$ odd natural numbers is $\ldots \ldots \ldots$

Yasmeen saves $Rs.\, 32$ during the first month,$Rs.\, 36$ in the second month,and $Rs.\, 40$ in the third month. If she continues to save in this manner,in how many months will she save $Rs.\, 2000$?

In the $AP: 10, 5, 0, -5, \ldots$,the common difference $d$ is equal to $5$. Justify whether the above statement is true or false.