Thread: Exponential Functions/Logs Questions -- Help!

2 .Assume that the number of viruses present in a sample is modeled by
the exponential function f(t) = 10t, where t is the elapsed time in
minutes.

How would you apply logarithms to determine when the sample will grow
to 5 billion viruses?

4. Maya has deposited $600 in an account that pays 5.64% interest, compounded continuously. How long will it take for her money to double.

I have the following:
A = Pe^rt
A = 600e^(5.64)(t)
1200 = 600e^(5.64)(t)
2 = e^(5.64)(t)
ln(2) = ln(e)^(5.64)(t)
ln(2) = 5.64t
(ln(2))/5.64 = t

Is this correct?

7. A computer is infected with the Sasser virus. Assume that it infects 20 other computers within 5 minutes; and that these PCs and servers each infect 20 more machines within another 5 minutes, etc. How long until 100 million computers are infected?

Originally Posted by MathGeek06

2 .Assume that the number of viruses present in a sample is modeled by
the exponential function f(t) = 10t, where t is the elapsed time in
minutes.

How would you apply logarithms to determine when the sample will grow
to 5 billion viruses?

I assume you mean

Solve

Remember

Using base 10 you get

Originally Posted by MathGeek06

4. Maya has deposited $600 in an account that pays 5.64% interest, compounded continuously. How long will it take for her money to double.

Try x

Originally Posted by MathGeek06

7. A computer is infected with the Sasser virus. Assume that it infects 20 other computers within 5 minutes; and that these PCs and servers each infect 20 more machines within another 5 minutes, etc. How long until 100 million computers are infected?

1+20+400..... This is a geometric series.

Thanks a tutor!

Is it possible that someone can be more specific in helping me answer the last question about the computer virus. I see that it is a geometric series, but I am still not sure how to go about getting the answer to the question.

first term a=1
common ratio r=20

Sum of first n terms

In this case

Solve that to get your answer.