Mastering Exponential Growth & Decay: 8th Grade Review

A bacteria culture doubles in size every 3 hours. If there are initially 500 bacteria, how many will there be after 12 hours?

• 1000

• 8000

• 16000

• 4000

A car's value decreases by 15% each year. If the car is worth $20,000 now, what will its value be after 3 years?

• $15,000

• $10,000

• $18,000

• $12,282.50

A tree grows at a rate of 5% per year. If the tree is currently 10 feet tall, what will its height be after 4 years?

• 11.25 feet

• 12.16 feet

• 10.5 feet

• 15 feet

A radioactive substance decays at a rate of 25% per hour. If you start with 80 grams, how much will remain after 2 hours?

• 45 grams

• 30 grams

• 60 grams

• 20 grams

A population of fish in a lake decreases by 10% each year due to overfishing. If there are currently 1,000 fish, how many will be left after 5 years?

• 800

• 450

• 700

• 590

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

• 1500.00

• 1000.00

• 1100.00

• 1216.65

A certain type of plant grows exponentially. If it grows to 3 feet in 2 weeks, how tall will it be in 6 weeks assuming the same growth rate?

• 27 feet

• 15 feet

• 9 feet

• 45 feet

A smartphone loses 20% of its value each year. If it is purchased for $800, what will its value be after 2 years?

• $640

• $720

• $512

• $400

A certain species of bacteria triples in number every 4 hours. If you start with 200 bacteria, how many will there be after 16 hours?

• 16200

• 6400

• 2400

• 800

A car depreciates in value according to the function V(t) = 25000(0.85)^t, where t is the number of years. What will the value of the car be after 5 years?

• 13000

• 9000

• 11092.5

• 15000