The number of bacteria in a sample quadruples every 24 hours. There are 20 bacteria in the sample initially. Write an equation to find b, the number of bacteria in the sample after d days.

This is an exponential growth problem of the form:

F=Ir^t we are told that the sample quadruples every day so

4=r^1 so

r=4 then the equation becomes:

F (t) = a4^t and we are told that the initial sample, a, is 20 so:

F (t) = 20 (4^t) and if we let t=days=d

F (d) = 20 (4^d)