Put these scenarios into a Category: Linear, Exponential, Or Neither

1- If the half-life of a substance is 2 days, what is the amount of the substance left at the end of 4 days?

2- The altitude of a hot air balloon and time when the hot air balloon takes off at 7500 feet above sea level and rises 180 feet every minute.

3-The cost of the rental space is $780 and the price per person for food is $9.75

4-The distance driven and total cost when a taxi driver charges $3 for the first mile and $2 for each additional mile.

5-The number of bacteria and time when a culture of 5000 bacteria is reduced by 50% every two hours.

6-The volume of a landfill and time given that the volume triples every five years.