The half-life of 234U, uranium-234, is 2.52 105 yr. If 98.6% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?

Answer 1

.986=e^(-.693t/2.52E5)

take the ln of both sides..

> -0.0140989244=-.693t/2.52E5
solve for t

t== 0.693147181*2.52E5/0.0140989244

I get a little over 12 million yars