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 1089275: 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(39630) About Me  (Show Source):
You can put this solution on YOUR website!
(Note that t=0 is for year 1988.)

y=p%2Ae%5E%28-kt%29
-
k=ln%282%29%2F6
k=0.1155
-
y=p%2Ae%5E%28-0.1155t%29
You want to find t, when p=1 and y=0.14.