We have the following:
To know how many times one grain is bigger than the other, we must calculate the quotient of them, as follows:
[tex]\frac{0.0046}{0.00005}=\frac{4.6\cdot10^{-3}}{5\cdot10^{-5}}=0.92\cdot10^{-3-(-5)}=0.92\cdot10^2=92[/tex]Therefore it is 92 times larger