Half life of plutonium?

Question

The half life of plutonium-234 is 9 hours. If 50 milligrams is present now, how much will be present in 4 days? Our book has the formula, I just dont know how to rearrange the problem/numbers to work out how the book says. Please help!

Answer 1

m = m₀*exp[-t*(ln2)/(t(1/2))] = (50 mg)*exp[-(4*24 hr)*(ln2)/(9 hr)] = 0,03076 mg

See also:

http://en.wikipedia.org/wiki/Radioactive_decay

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Answer 2

it has greater weight yet not greater protons, so it has greater neutrons, this suggests that the necleaus is greater good because of the fact there's a much better distance between protons(that are attempting to push one yet another away)-