algebra
posted by Anonymous on .
The halflife of 234U, uranium234, 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?

.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 
.977=1e^(.693t/thalf)
take lne of each side.
ln.977=.692t/th
t= thalf*ln.977/.693