Answer
a. 800 bacteria
b. 1.41$\times$$10^{16}$ bacteria
Work Step by Step
A population of bacteria doubles every 30 minutes, which can be represented as $p(x)=50$$\times$$2^{x}$. $x$ is the number of 30-minute periods:
a. In 2 hours, there are 4 30-minute periods, so $p(x)=50$$\times$$2^{4}$$=800$
b. In 1 day, there are 48 30-minute periods, so $p(x)=50$$\times$$2^{48}$$=1.41$$\times$$10^{16}$
