A balloon of diameter 20 metre weighs 100kg . Calculate its pay-load if it is filled with He at 1.0atm and $27^{\large\circ}C$ . Density of air is 1.2 $kgm^{-3}$ . [$R = 0.082dm^3\;atm\; K^{-1}\;mol^{-1}$]

Question

$\begin{array}{1,1}(a)\;424.67\times10^4g\\(b)\;4.2467\times10^4g\\(c)\;42.467\times10^4g\\(d)\;0.424\times10^4g \end {array}$

Comments

Why we divide the air displaced by 10*3 and multiply too?