Mastering Exponential Decay & Compound Interest for Grade 9

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

• 16000

• 1000

• 4000

• 8000

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

• $10,000

• $15,000

• $8,500

• $12,282.50

You invest $1,000 in a savings account that offers an annual interest rate of 5%, compounded annually. How much money will you have after 4 years?

• 1000.00

• 1300.00

• 1215.51

• 1100.00

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

• 5 grams

• 10 grams

• 40 grams

• 20 grams

A population of fish in a lake decreases by 10% each year due to overfishing. If there are currently 1,200 fish, how many will be left after 2 years?

• 1,200

• 972

• 1,080

• 1,000

You deposit $2,500 into an account that earns 3% interest compounded quarterly. How much will you have in the account after 5 years?

• $2,904.00

• $3,000.00

• $2,500.00

• $2,750.00

A tree's height decreases by 20% each year due to disease. If the tree is currently 15 feet tall, what will its height be after 2 years?

• 8 feet

• 9.6 feet

• 10 feet

• 12 feet

You take out a loan of $5,000 with an interest rate of 6% compounded annually. How much will you owe after 3 years?

• $5,955.08

• $6,000.00

• $5,200.00

• $5,500.00

A certain type of plant grows at a rate of 25% per month. If you start with 10 plants, how many will you have after 4 months?

• 30

• 20

• 24

• 15

A car depreciates in value by 18% each year. If the car was purchased for $30,000, what will its value be after 2 years?

• $25,000

• $22,500

• $20,172

• $15,000