by using

we get

now just solve for t, using logarithims

i think thats how you set it up, if not change the 1 and 0.1 to 100 and 10

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- October 25th 2008, 06:36 PM #1

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## -HELP-

After the release of radioactive material into the atmosphere from a nuclear power plant at Chernobyl (Ukraine) in 1986, the hay in Austria was contaminated by iodine 131 (half-life 8 days). If it is alright to feed the hay to cows when 10% of the iodine 131 remains, how long do the farmers need to wait to use this hay?

- October 25th 2008, 09:27 PM #2

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- October 25th 2008, 09:40 PM #3

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- October 25th 2008, 09:49 PM #4

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No= Original

So we know that the orginal has to be 100% so we have to let it equal 1, or we can let it equal 100, it doesn't matter

Nt = Amount leftover

So we want 10% to be leftover so it is usable to feed the cows thats why we let it equal .1 or 10, it doesnt matter,

t1/2 = constant half-life decay

Since it tells us in the questions that radiocative decay in the hay is 8 days, we can let this be 8 then when we solve for t

We can find out how many days the hay hasn't to not be eaten for it to decay to 10% so it can be eatable for the cows

I hope that clears it up

you can always use the beloved,

Half-life - Wikipedia, the free encyclopedia

to clear things up

- October 25th 2008, 10:01 PM #5

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- October 25th 2008, 10:05 PM #6

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you forgot the 1, and u can bring the exponent down, by properties of logarithms, then isolate for t,

if you need to know the logarithms:

Logarithm - Wikipedia, the free encyclopedia

- October 25th 2008, 10:10 PM #7

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- October 25th 2008, 10:14 PM #8

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