Question

A type of bacteria in a Petri dish doulbles every hour. If there were 1,073,741,824 bacteria after 24 hours, how many were there to start with?

Answer 1

It multiply in a Geometric Progression
1st Term=a= ?
common ratio= r= 2
last term=l= 1073741824
no. of terms in GP= 25

1073741824= a*r^n-1
1073741824= 2^24 * a
a= 1073741824/ 2^24
a=64 bacteria