Rewriting Exponential Functions Answers

The amount of radioactive element remaining, r, in a 100-mg sample after d days is represented using the equation . What is the daily percent of decrease?

Jillana takes a single dose of medication that remains in her body according to the equation r = 200(0.75)d, where r represents the amount of medication remaining after d days. If Jillana had taken the medication four days earlier, the amount of medication remaining in her system relative to the amount that remains in her system after d days would be represented using the equation r2 = 200(0.75)d + 4. Which of the following is an equivalent equation?

The half-life of a radioactive element is five years. A scientist has 18 grams of the element. The equation representing the number of grams, g, after x years is . What is the annual rate of decay?

Leela invests $500 at 4.5% interest according to the equation , where Vl is the value of the account after t years. Adele invests the same amount of money at the same interest rate, but begins investing two years earlier according to the equation . The total value of Adele’s account is approximately what percent of the total value of Leela’s account at any time, t?

Karey is prescribed 600 mg of a medication that decays at a rate of 40% per day, d, according to the equation , where m is the amount of medication remaining in his body. Noelle takes the same medication five days earlier. The number of milligrams of medication in Noelle’s body is about what percentage of the number of milligrams in Karey’s body at any time after they have both taken the medication?

The value, V, of Kalani’s stock investments over a time period, x, can be determined using the equation . What is the rate of increase or decrease associated with this account?

Nolan began a savings account three years ago. He invested $100 at a 2% interest rate according to the equation Vn = 100(1.02)x, where Vn is the value of his account after x years. Anias started an account today. She invested $100 at a 2% interest rate according to the equation Va = 100(1.02)x–3, where Va is the value of her account. Let’s say Anias started saving at the same time Nolan did, three years ago. Approximately how much money would she have had to invest to have the same amount of money she has now?