$\mathrm{Cr}_2 \mathrm{O}_3$ Amphoteric oxide

In $\mathrm{CrO}, \mathrm{Cr}$ exist as $\mathrm{Cr}^{+2}$ and have $\mu$ only $=4.90$

In $\mathrm{Cr}_2 \mathrm{O}_3, \mathrm{Cr}$ exist as $\mathrm{Cr}^{+3}$ and have $\mu$ only $=3.87$

Sum of spin only magnetic moment

$=4.90+3.87=8.77$

$\mu_{\text {only }}=877 \times 10^{-2}$

Ans. $877$