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# Half-Life Problem: Pre-Calc. Packet help... again. watch

1. So I'm back again after asking a painfully simple question last time, and i have a feeling this one's even simpler, but here we go anyway...

So here's the question:
"The half-life of Cobalt-60 is about 5,000 years. this means that every 5,000 years, half the remaining atoms will decay into another element. If a sample contains 40 grams of Cobalt-60 in the year 2005, how much Cobalt-60 will be left in the sample in the year 2550?"

Now in my class that I took this past year (Algebra II with Trigonometry), we literally did ONE half-life problem, so it's most definitely not my forte. Anywho, with some work and thought I came up with a final answer of 37.09g, which just doesn't seem right. Maybe it is? I don't know, any help's appreciated.

Again, sorry if it's a simple question, but maybe I'm just not thinking straight because it's 12:13am here (Wisconsin, USA).
2. I'd start by stating the equation for a quantity undergoing exponential decay, expressing the mass at time t, in terms of the initial mass.

Then use your knowledge of the half life to work out the constant.

See what you can do with that.
3. (1/2)^((2550-2005)/5000) * 40 = 37.08922186...

37.1g to 3sf

yes you are correct
4. mk thanks. it just seemed a little high but at least now i have a confirmation. thanks.

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