posted by meghan .
The half-life of plutonium-234 is 9 hours. If 40 milligrams is present now, how much will be present in 4 days? (Round your answer to three decimal places.)
after h hours,
40 * (1/2)^(h/9)
That's because for every 9 hours, the amount is multiplied by 1/2
so, after 4 days = 96 hours, we will have
40 * (1/2)^(96/9) = .0246 mg