so, after 30 mins we have:
100*2
After 1 hour: 100*2*2, etc
the number of 2s will be the number of time they will divide: 3 hrs divided by 0.5 hour: this is six times.
So the final number of cells will be:
[tex]100* 2^{6} =100 *2*2*2*2*2*2= 100 *8*8=100 *64=6400[/tex]
So after 3 hrs there will be 6400 cells there!