Here r=radix number or base
integer part n digits
fraction part m digits
N= positive given number.
$\left ( i \right ) 325$
$10^{3}-10^{0}-325=999-325=674$
$\left ( ii \right )325.893$
$10^{3}-10^{-3}-325.893=999.999-325.893=674.217$
Similar for $(iii)$ and $(iv)$ too.-ve willnot have any extra effect on numbers
Ref: Page 27 here