[+rep] Exponential Decay problems

[Leet]

FIRST PROBLEM

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SECOND PROBLEM

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Show work/explanation/calculations for both for full rep. Thanks.

For whomever solves 'em, I will also draw a picture

[bamag]

@(you need an account to see links) Not sure if I did 2nd one correctly but I'm pretty sure about #1
1.
A(T) = Ao * e^(kT)
.5A = A * e^(kT)
.5 = e ^ (kT)
ln .5 = kT
-.693 = 5730k
k = -.000121
.91 =e^(-.000121T)
ln .91 = -.000121T
-.0943 = -.000121T
T= 779.4 years
The table could not have belonged to King Arthur.

2.
A(T) = Ao * e^(kT)
93.4=94.6 * e^(kT)
.987 = e^(kT)
ln .987 = k(1)
-.0131 = k
94.6 = 98.6 * e ^ (kT)
.96 = e^(kT)
ln .96 = kT
-.041 = -.0131T
T= 3.1
Noon - 3.1 = ~9AM