It's Growing

I may turn this bloggin thang into a math problem.

We started with 1 post on March 15th and by March 20th we had 14 posts. Assuming exponential growth, create a mathematical model that would predict the number of posts for any given date in the future. Use your model to predict the number of posts posted by March 31. How would your answer change if we assume that the growth followed a logistic model instead?

That makes each of you precalculus fodder.