If ${}^n P_r = 30240$ and ${}^n C_r = 252$,then the ordered pair $(n, r)$ is equal to

Choanocytes are present in

If $\theta$ is the angle between the curves $xy=2$ and $x^2+4y=0$, then $\tan \theta$ is equal to:

Why does molten sodium chloride conduct electricity?

A linear octasaccharide $($molar mass $=1024 g mol ^{-1} )$ on complete hydrolysis produces three monosaccharides: ribose, $2-$deoxyribose and glucose. The amount of $2-$deoxyribose formed is $58.26 \%( w / w )$ of the total amount of the monosaccharides produced in the hydrolyzed products. The number of ribose unit$(s)$ present in one molecule of octasaccharide is $.....$
Use : Molar mass $($in g $mol ^{-1} )$: ribose $=150,2-$deoxyribose $=134$, glucose $=180$; Atomic mass $($in amu$): H =1, O =16$

$S_1, S_2, \ldots, S_{10}$ are the speakers in a conference. If $S_1$ addresses only after $S_2$,then the number of ways the speakers address is