The $n^{th}n^\{th\}$ term of the series 1.3 + 3.5 + 5.7 + …………….. is

If n arithmetic means are inserted between a and b, then the common difference is …………

Sum to n terms of 1.2.3 + 2.3.4 + 3.4.5 + ……………… is .

$\frac{1+2+3+\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}+n}{1+3+5+\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}+(2n-1)}=\backslash frac\{1+2+3+.......+n\}\{1+3+5+.....+(2n-1)\}\; =$

If the common difference of an A.P is 1 and 6th term is $\frac{(4co{s}^2\alpha +1)}{co{s}^2\alpha }\backslash frac\{(4\; \backslash ,\; cos^2\; \backslash alpha+1)\}\{cos^2\; \backslash alpha\}$ , then first term is

The sum of all two digit odd numbers is

Sum of n terms of 1 + 4 + 13 + 40 + ……………… is

Sum of n terms of 2.3 + 3.4 + 4.5 + ………………. is

If 2nd term of a G.P is 24 and 5th term is 81, then first term is

The common ratio of  $2+\frac{2}{3}+\frac{2}{9}+\frac{2}{27}+\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}\mathrm{.}2\; +\; \backslash frac\{2\}\{3\}\; +\; \backslash frac\{2\}\{9\}\; +\; \backslash frac\{2\}\{27\}+.........$ is