Real-World Growth & Decay: Word Problems for 8th Graders

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

• 2000

• 1000

• 4000

• 3000

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

• $16,000

• $18,500

• $17,000

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?

• 10.5 feet

• 13.0 feet

• 15.0 feet

• 12.16 feet

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

• 1100.00

• 1000.00

• 1216.65

A certain species of fish in a lake decreases by 20% each year due to pollution. If there are currently 1,000 fish, how many will be left after 3 years?

• 800

• 400

• 600

• 512

A town's population is 10,000 and is growing at a rate of 8% per year. What will the population be in 5 years?

• 12000

• 15800

• 13500

• 14693

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

• 60 grams

• 45 grams

• 30 grams

• 20 grams

A smartphone loses 30% of its value each year. If it was purchased for $800, what will its value be after 3 years?

• 680

• 400

• 560

• 274.4

A certain plant species grows exponentially, doubling in size every month. If it starts at 2 inches, how tall will it be after 6 months?

• 256 inches

• 128 inches

• 64 inches

• 32 inches

A loan of $5,000 has an interest rate of 6% compounded annually. How much will be owed after 3 years?

• $5,500.00

• $5,955.08

• $6,300.00

• $4,800.00