The  number  of  milligrams  of drug   that are  in 45 ml  of a 1.5%  w/v   solution
is 0.675   mg
           calculation
 this is calculated using  ( %M/V =  mass  in milligrams/   volume  x100    formula )
%M/V  = 1.5 %
volume  = 45 ml
mass = ?
convert  %(m//v)  into  fraction  = 1.5/100    and let  the mass be represented by  y
 therefore  1.5/100  =     y/45
cross  multiplication
=67.5 =  100 y
divide both  side by  100
y=0.675  mg