Question

which situation could be modeled by using a linear function ?
1) a bank account balance that grows at a rate of 5% per year compounded annually
2) a population of bacteria that doubles every 4.5 hours
3) the cost of the cell phone service that charges a base amount plus 20 cents per minute
3) the concentration of medicine in a persons body that decays by a factor of one- third every hour

Answer 1

Nuimber-3 (the number-3 that talks about cell phone service)
is the only choice that produces a straight pine on a graph. 
The others all produce curves.

Answer 2

3) the cost of the cell phone service that charges a base amount plus 20 cent per minute