Posted by **Anonymous** on Saturday, January 28, 2012 at 3:11pm.

The half-life of 234U, uranium-234, is 2.52 105 yr. If 97.7% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?

- algebra -
**Damon**, Saturday, January 28, 2012 at 4:02pm
.5 = e^2.52*10^5 k

ln .5 = 2.52 * 10^5 k

k =-2.75*10^-6

ln .977 = -2.75*10^-6 t

t = 8460 years

= 8,000 years

- algebra -
**bobpursley**, Saturday, January 28, 2012 at 4:04pm
.977=1e^(.693t/thalf)

take lne of each side.

ln.977=.692t/th

t= thalf*ln.977/.693

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