Mastering Exponential Growth & Decay: Grade 9 Quiz

A population of bacteria doubles every 3 hours. If there are initially 500 bacteria, how many will there be after 9 hours?

• 1000

• 4000

• 3000

• 2000

A car's value decreases by 15% each year. If the car is currently worth $20,000, what will its value be after 2 years?

• $14,450

• $18,000

• $12,000

• $16,000

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

• 12.16 feet

• 11 feet

• 15 feet

• 10.5 feet

A radioactive substance has a half-life of 5 years. If you start with 80 grams, how much will remain after 15 years?

• 10 grams

• 40 grams

• 5 grams

• 20 grams

A savings account earns 4% interest compounded annually. If you deposit $1,000, how much will you have in the account after 3 years?

• 1000.00

• 1200.00

• 1100.00

• 1124.86

A certain species of fish in a lake is decreasing at a rate of 10% per year. If there are currently 1,200 fish, how many will be left after 5 years?

• 709

• 950

• 600

• 800

A new technology is adopted by 30% of the population each year. If 1,000 people use it in the first year, how many will use it after 3 years?

• 2197

• 2500

• 1500

• 1800

A tree's height increases exponentially, reaching 50 feet in 10 years. If it started at 5 feet, what is the growth factor?

• 10^(1/10)

• 2^(1/10)

• 5^(1/10)

• 10^(1/5)

A car depreciates in value according to the formula V(t) = V0 * e^(-kt). If the initial value is $25,000 and k = 0.1, what will the value be after 5 years?

• 20000

• 18000

• 12500

• 15163.75

A certain type of bacteria grows exponentially. If the population is 200 and grows to 1,600 in 4 hours, what is the growth rate per hour?

• 0.51985

• 0.30103

• 0.69315

• 0.43429