SOLUTION: After the release of radioactive material into the atmosphere from a nuclear power plant in a country in 1988​, the hay in that country was contaminated by a radioactive isot

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Question 1088827: After the release of radioactive material into the atmosphere from a nuclear power plant in a country in 1988​, the hay in that country was contaminated by a radioactive isotope​ (half-life 6 ​days). If it is safe to feed the hay to cows when 14​% of the radioactive isotope​ remains, how long did the farmers need to wait to use this​ hay?
The farmers needed to wait approximately
_____ days for it to be safe to feed the hay to the cows.
​(Round to one decimal place as​ needed.)
Answer by josgarithmetic(39616) About Me  (Show Source):
You can put this solution on YOUR website!
Exponential Decay,
just the beginning,
y=p%2Ae%5E%28-kx%29
-
1%2F2=1%2Ae%5E%28-6k%29

ln%281%2F2%29=-6k
-6k=-ln%282%29
k=ln%282%29%2F6
k=0.1155

MODEL, y=p%2Ae%5E%28-0.1155x%29;

If x is time since initial release, IN DAYS, and p=1, and y=0.14, then solve for x.