3. Write a function that models 400 mg of a substance that has a half-life of 84 days.

4. Using the same data in #3, how much of the substance will be left after 110 days?

5. Ahmed invests $400 into a back account that pays 3.5% interest annually. How long will
it take Ahmed's account to accumulate $500?

3. The model for a substance of 400 mg with a half-life of 84 days is:

4. 160 mg.

5. It will take 7 years for Ahmed's account to accumulate $500.

Step-by-step explanation:

3. We can write a model for the substance with exponential decay as:

We know that at time t=0, the mass is 400 mg.

We also know that the half-life is 84 days, so at t=84 days, the mass will be 400/2=200 mg.

The model for a substance of 400 mg with a half-life of 84 days is:

4. After 110 days the substance will have a mass of y=160 mg.

5. The amount that Ahmed's will acumulate in function of the years (n) can be written as:

We can calculate how many years it will take for the Amhed's account to acumulate $500 as:

It will take 7 years for Ahmed's account to accumulate $500.

50 min

step-by-step explanation:

they will be decreasing both their times in half

60 / 2 = 30

40/2 = 20

30 + 20 = 50