Question

a culture initially contains 200 bacteria. if the number of bacteria doubles every hour how many bacteria will be in the culture qt the end of 12 hours

Answer 1

using the formula for an exponential function:
y=b*a^x

Insert you values:
y=200*2^x

b=200 because there are 200 bacteria in the beginning
a=2 because 200%/100%=2. (200 bacause it doubles)

Insert 20 in x and solve for y:
y=200*2^13=819200

So after 12 hours there are 819200 bacteria.

I hope that helped.