Question 693912: How long would it take 100,000 grams of radioactive iodine, which has a half-life of 60 days, to decay to 25,000 grams? Use the formaula N=N (1/2)^t, where N is the final amount of the substance, N is the initial amount, and t represents the number of half-lives.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! How long would it take 100,000 grams of radioactive iodine, which has a half-life of 60 days, to decay to 25,000 grams? Use the formaula N(t)= N (1/2)^t, where N is the final amount of the substance, N is the initial amount, and t represents the number of half-lives.
25000 = 100000*(1/2)^t
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(1/4) = (1/2)^t
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t = 2 half-lives = 2*60 days = 120 days
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Cheers,
Stan H.
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