f=1X2^6=64
First find out the number of generation, let one=n( no. of generation)
n=total time of division/time taken for one division
i.e. 2 hours = 120min/20min=6
Answer any question with this given formula
f=ix2^n where :
f=final number of bacteria
i=initial number of bacteria
n=6
f=1X2^6=64