Decay and Growth: Solving Exponential Models in 8th Grade

A bacteria culture starts with 500 bacteria and decays at a rate of 10% per hour. How many bacteria will remain after 3 hours?

• 300

• 500

• 450

• 364

A car's value decreases by 15% each year. If the car was originally worth $20,000, what will its value be after 4 years?

• $8,500.75

• $10,448.13

• $15,000.00

• $12,000.00

A tree grows at a rate of 5% per year. If the tree is currently 10 feet tall, what will its height be after 5 years?

• 8 feet

• 10 feet

• 15 feet

• 12.76 feet

A radioactive substance has a half-life of 3 years. If you start with 80 grams, how much will remain after 9 years?

• 10 grams

• 15 grams

• 20 grams

• 5 grams

A population of fish in a lake decreases by 20% each year due to overfishing. If there are currently 1,000 fish, how many will be left after 2 years?

• 500

• 720

• 800

• 640

A savings account earns 4% interest compounded annually. If you deposit $1,000, how much will you have in the account after 5 years?

• 1100.00

• 1300.00

• 1000.00

• 1216.65

A certain species of plant doubles in population every year. If there are 50 plants now, how many will there be in 4 years?

• 400

• 200

• 800

• 100

A car depreciates in value according to the equation V(t) = 20000(0.85)^t, where V is the value and t is the number of years. What will the value be after 5 years?

• 8874.00

• 7500.75

• 12000.50

• 10000.00

A certain type of mold grows exponentially. If it starts with 10 spores and triples every day, how many spores will there be after 3 days?

• 150

• 1000

• 90

• 270

A town's population is 10,000 and is decreasing at a rate of 3% per year. What will the population be in 5 years?

• 9000

• 8587

• 9500

• 8200