Exponential Growth & Decay: Math Challenges for 7th Graders

A population of rabbits doubles every year. If there are 50 rabbits now, how many will there be in 3 years?

• 400 rabbits

• 200 rabbits

• 800 rabbits

• 100 rabbits

A bacteria culture starts with 200 bacteria and grows at a rate of 25% per hour. How many bacteria will there be after 4 hours?

• 400

• 600

• 488

• 350

A tree grows 15% each year. If the tree is currently 120 cm tall, what will its height be after 2 years?

• 175 cm

• 145 cm

• 130 cm

• 158.7 cm

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

• $7,680

• $10,000

• $5,000

• $12,000

A savings account has $1,000 and earns 5% interest compounded annually. How much money will be in the account after 5 years?

• $1,276.28

• $1,100.00

• $1,500.00

• $1,200.00

A certain species of fish in a lake grows at a rate of 10% per year. If there are currently 500 fish, how many will there be in 4 years?

• 732

• 800

• 900

• 600

A town's population is 10,000 and is decreasing by 3% each year. What will the population be in 5 years?

• 8500

• 8000

• 8638

• 9000

A plant grows at a rate of 12% per month. If it is currently 30 cm tall, how tall will it be in 6 months?

• 59.21 cm

• 45.00 cm

• 72.50 cm

• 50.00 cm

A loan of $2,000 has an interest rate of 8% per year. How much will be owed after 3 years if the interest is compounded annually?

• $3,000.00

• $2,400.00

• $2,519.42

• $2,000.00

A certain type of mold grows at a rate of 50% every day. If you start with 10 grams of mold, how much will there be after 3 days?

• 50 grams

• 40 grams

• 33.75 grams

• 20 grams