Train A leaves Paris and travels at a constant speed of 75 mph toward Pisa. At the same time, Train Bleaves Pisa headed toward Paris at a constant speed of 50
mph. Let x represent time traveled in hours and let y represent miles from Paris. If
Paris and Pisa are 500 miles apart, when will the two trains pass each other?
Train A Traveling 75 mph
WH
y = 75x
500 miles
Paris, France
Pisa, Italy
Train B - Traveling 50 mph
y = 500 - 50x

The biologist has a second culture to examine. she knows that the population of the culture doubles every 15 minutes. after 1 hour and 15 minutes, her assistant found that 80,000 bacteria were present. a) what was the size of the initial population? b) predict the size of the culture at t=3 hours. what was the size of the population at 40 minutes? explain and justify your answers. c) create a graph of the population as a function of time. find an equation that can be used to predict the size of the population at any time t. d) examine the rate at which the bacteria culture is growing. how fast is the culture growing after 1 hour? after 1.5 hours? after 2 hours? use a time interval of h = 0.01 hours to estimate these rates. interpret these rates in terms of the context of the problem situation. how do these three rates compare?