Question

Half life of 1000 years. How long would it take to decay to 40% of that amount.

Answer 1

too damn long

Answer 2

solve
\[.4=(\frac{1}{2})^{\frac{t}{1000}}\] for t

Answer 3

via
\[\ln(.4)=\frac{t}{1000} \ln(.5)\]
\[t=1000\times \frac{\ln(.4)}{\ln(.5)}\]

Answer 4

right mathgirl?

Answer 5

totally

Answer 6

hmmm. what would be the next step to get it in years

Answer 7

whip out a calculator and type it in

Answer 8

i did. its coming up undefined. let me try again

Answer 9

i get 1322 rounded

Answer 10

oh yes. i put it in wrong. ok. thanks.

Answer 11

yw