Find the correct alternative
$1,5,13,29,61,125,?$

Q. $(2^{51}+2^{52}+2^{53}+2^{54}+2^{55})$ is divisible by

Q. Observe the following pattern for obtaining the sums, then find the sum of numbers from 781 to 790?
$1+2+3+4+5+6+7+8+9+10=55$
$11+12+13+14+15+16+17+18+19+20=155$
$21+22+23+24+25+26+27+28+29+30=255$
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$101+102+103+104+105+106+107+108+109+110=1055$
$251+252+253+254+255+256+257+258+259+260=2555$

Q. Mark the correct alternative in the following question:

$$\begin{gathered} {\left({25}^2-{15}^2\right)}^{\frac{3}{2}}= \\ \left(\mathrm{a}\right)4000\left(\mathrm{b}\right)8000\left(\mathrm{c}\right)3125\left(\mathrm{d}\right)1024 \end{gathered}$$

Q. Mark the correct alternative in each of the following:

The reciprocal of the fraction $2\frac{3}{5}$ is

(a) $2\frac{5}{3}$ (b) $\frac{13}{5}$ (c) $\frac{5}{13}$ (d) $2\frac{2}{5}$