Answer
$m=4.93 \times 10^{-5} \mathrm{~kg} $
Work Step by Step
Since $1.0 \mathrm{~kg}$ of TNT gives off $4.6 \mathrm{MJ}$, the TNT equivalent of the pellet is
$
m=\frac{227 \mathrm{~J}}{4.6 \times 10^6 \mathrm{~J}}=\\4.93 \times 10^{-5} \mathrm{~kg} .
$
