Exponential Growth and Decay Solve for Time

What is the decay factor in the following model? A=1200(.85)⁶

• 1200

• -.15

• .85

• .15

The number of mosquitoes at the beginning of the summer was 4,000. The population of mosquitoes is expected to grow at a rate of 25% a month. How many mosquitoes will there be after 4 months?

• 9766

• 9006

• 9765

• 5433

Suppose a culture of bacteria begins with 5000 cells and dies by 30% each year. Write an equation that represents this situation.

• y=5000(0.7)^x

• y=30(5000)^x

• y=5000(1.3)^x

• y=5000x^x

An antibiotic is introduced into a colony of 12,000 bacteria during a laboratory experiment. The colony is decreasing by 14.9% per minute. Which function can be used to model the number of bacteria in the colony after x minutes?

Suppose you deposit $500 in a savings account that earns 1% interest compounded continuously. Find the balance in your account after 2 years.

• $510.05

• $3694.53

• $510.10

• $605

Twenty years ago, Mr. Davis purchased his home for $160,000. Since then, the value of the home has increased about 5% per year. How much is the home worth today?

• $176,783.29

• $424,527.63

• $57,357.75

• $532,041,076.80

There were 417 cell phones sold at an electronics store in January. Since then, cell phone sales at this store have increased at a rate of 3.75% per month. At this rate of growth, which function can be used to determine the monthly cell phone sales x months after January?

Riley invested $1,000 in savings bonds. If the bonds earn 6.75% interest compounded semi-annually, how much total will Riley earn in 15 years?

• $1,584.62

• $2,651.39

• $2,706.86

• $1,825.10

A population of fish starts at 8,000 and DECREASES by 6% per year. What is the population of fish after 10 years?

• 14327

• 4308

• 4839

The original value of a painting is $1400, and the value increases by 9% each year. Write an exponential growth function to model this situation.

• y=1400(1.09)^x

• y=1.09(1400)^x

• y=1400(.91)^x