Real-World Growth and Decay Problems for Grade 7

A plant grows at a rate of 5% per week. If the plant is currently 20 cm tall, how tall will it be after 3 weeks?

• 25 cm

• 30 cm

• 23.15 cm

• 18 cm

A bacteria culture doubles in size every hour. If you start with 100 bacteria, how many will there be after 4 hours?

• 1600

• 2000

• 800

• 400

A car depreciates in value by 15% each year. If the car is worth $20,000 now, what will its value be after 2 years?

• $12,000

• $16,000

• $14,450

• $18,000

A radioactive substance decays at a rate of 10% per hour. If you start with 500 grams, how much will remain after 3 hours?

• 300 grams

• 450 grams

• 500 grams

• 364.5 grams

A tree loses 20% of its leaves each autumn. If it has 1,000 leaves at the start of autumn, how many leaves will it have left after one autumn?

• 600

• 900

• 750

• 800

A savings account earns 4% interest compounded annually. If you deposit $1,000, how much will you have after 2 years?

• $1,081.60

• $1,040.00

• $1,120.00

• $1,000.00

A population of fish in a lake decreases by 25% each year due to overfishing. If there are 800 fish now, how many will be left after 2 years?

• 600

• 300

• 450

• 200

A smartphone loses 30% of its value as soon as it is purchased. If the original price is $600, what is its value after the first year?

• $480

• $500

• $300

• $420

A certain species of plant grows by 10% each month. If you have 50 plants, how many will you have after 6 months?

• 60

• 75

• 89

• 100

A city’s population is projected to decrease by 5% each year. If the current population is 50,000, what will the population be in 3 years?

• 38000

• 45000

• 40000

• 42869