Exponential function Word Problem?

Question

The link is below so you can view clearly with the problem.
Please show work and explain how you approached solving this problem so i can learn.
http://docs.google.com/Doc?id=dg4zw6jf_0fkcjznhs

Exponential function and/or logarithmic function

Answer 1

Well, A(n) = A0e^-0.35n represents the size of the wound after n days.
The question says the wound is 100 square millimeters in the beginning, and we want to know how long it takes to be half its size - 50 square millimeters.
To find that we need to set the equation to equal 50 -
50 = 100e^-0.35n
Divide both sides by 100 =
.5 = e^-0.35n.
take the natural log of both sides (eliminates the e - the natural log of e is 1, and the rule for taking a log of a number with exponent says u multiply the exponent by the log of the number for example the log of 10^2 (100) = 2*log 10 = 2) =
ln(.5) = -0.35n==> -0.6931 =-0.35n
divide both sides by -0.35 =
1.9804 days ~ 2 days.
hope this helps!

Answer 2

If it decreases 3% a twelve months, then each and every twelve months there is one hundred - 3 = 97% left, that's 0.97 as a decimal. S the equation is (t = years) f(t) = one hundred twenty,000 (0.97)^t In 10 years, put in 10 for t and do it out on a calculator.

Answer 3

50 = 100 e-.35^n [50 is 1/2 of original area of 100]
.5 = e^-.35n [Divide both sides by 100]
ln (.5) = ln (e^-.35n) [because ln e^x = x]
ln(.5) = -.35n
n = (ln.5)/-.35 days