Mastering Exponential Growth & Decay: Logarithmic Challenges

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

• 20 grams

• 5 grams

• 40 grams

• 10 grams

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

• 8000

• 1000

• 4000

• 16000

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

• $10,240

• $12,500

• $8,000

• $15,000

A certain medication is effective for 6 hours and its effectiveness halves every hour. If the initial effectiveness is 100%, what will be the effectiveness after 4 hours?

• 12.5%

• 50%

• 25%

• 6.25%

A tree grows at a rate of 10% per year. If the tree is currently 2 meters tall, what will its height be after 5 years?

• 4.00 meters

• 2.00 meters

• 5.00 meters

• 3.22 meters

A population of fish in a lake is currently 1,000. If the population decreases by 25% each year, how many fish will be left after 2 years?

• 562

• 750

• 800

• 900

A certain type of mold grows exponentially and doubles in size every 4 days. If you start with 10 grams, how much will you have after 16 days?

• 80 grams

• 40 grams

• 160 grams

• 200 grams

A certain isotope has a half-life of 10 years. If you have 50 mg of the isotope, how much will remain after 30 years?

• 3.125 mg

• 12.5 mg

• 25 mg

• 6.25 mg

A savings account earns 5% interest compounded annually. If you deposit $1,000, how much will you have after 10 years?

• 1628.89

• 2000.00

• 1500.00

• 1200.50

A certain species of plant grows to 80% of its maximum height in 4 years. If its maximum height is 2 meters, what will its height be after 4 years?

• 1.2 meters

• 1.8 meters

• 2.0 meters

• 1.6 meters