Mastering Decay Equations and Factors in Exponential Decay

A radioactive substance has a half-life of 5 years. If you start with 80 grams, how much will remain after 15 years? Write the decay equation and identify the decay factor.

• 10 grams

• 5 grams

• 20 grams

• 40 grams

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

• $10,000

• $7,680

• $9,600

• $8,000

A population of bacteria decreases by 30% every hour. If there are initially 1,000 bacteria, how many will remain after 4 hours? Write the decay equation and identify the decay factor.

• 1000

• 800

• 500

• 240

A certain type of medicine loses 25% of its effectiveness every hour. If a patient takes a dose of 200 mg, how much will be effective after 3 hours? Write the decay equation and identify the decay factor.

• 150 mg

• 84.375 mg

• 100 mg

• 50 mg

A tree loses 10% of its leaves each autumn. If it starts with 500 leaves, how many leaves will it have after 2 autumns? Write the decay equation and identify the decay factor.

• 405

• 400

• 450

• 350

A certain type of fish population decreases by 15% each year due to overfishing. If the initial population is 2,000, what will the population be after 5 years? Write the decay equation and identify the decay factor.

• 500

• 887

• 1500

• 1200

A smartphone battery loses 5% of its charge every hour. If the battery starts at 100%, how much charge will be left after 6 hours? Write the decay equation and identify the decay factor.

• 85%

• 73.51%

• 50%

• 60%

A certain chemical decays at a rate of 12% per day. If you start with 500 grams, how much will remain after 10 days? Write the decay equation and identify the decay factor.

• 200 grams

• 75 grams

• 350 grams

• 157 grams

A town's population decreases by 8% each year. If the current population is 50,000, what will the population be in 4 years? Write the decay equation and identify the decay factor.

• 36780

• 45000

• 40000

• 32000

A piece of wood shrinks by 4% in volume each year due to drying. If the initial volume is 1,000 cm³, what will the volume be after 3 years? Write the decay equation and identify the decay factor.

• 884.736 cm³

• 900 cm³

• 950 cm³

• 800 cm³