The first term of an $A.P. $ is $2$ and common difference is $4$. The sum of its $40$ terms will be
$3200$
$1600$
$200$
$2800$
If ${a_1} = {a_2} = 2,\;{a_n} = {a_{n - 1}} - 1\;(n > 2)$, then ${a_5}$ is
Find the $9^{\text {th }}$ term in the following sequence whose $n^{\text {th }}$ term is $a_{n}=(-1)^{n-1} n^{3}$
If the sum of $\mathrm{n}$ terms of an $\mathrm{A.P.}$ is $n P+\frac{1}{2} n(n-1) Q,$ where $\mathrm{P}$ and $\mathrm{Q}$ are constants, find the common difference.
The sum of all natural numbers between $1$ and $100$ which are multiples of $3$ is
If the first, second and last terms of an $A.P.$ be $a,\;b,\;2a$ respectively, then its sum will be