The growth of the virus is considered exponential.
Thus the expression is,
[tex]N=N_oe^{kt}[/tex]Given,
A virus takes 16 days to grow from 100 to 190.
Thus,
[tex]190=100e^{16k}[/tex]Putting ln on both side we have
ln(190/100)=16k
0.64=16k
k=0.04
Similarly,
[tex]760=100e^{0.04t}[/tex]Solving,
ln(760/100)=0.04t
t=50.70
Thus required days is 51 (rounding off to whole number)