Question 566146
The half-life of 234U, uranium-234x10to the 5th power year.
 If 98.1% of the uranium in the original sample is present, what length of time(to the nearest thousand years has elapsed?
:
The radioactive decay formula: A = Ao*2^(-t/h)
where:
A = resulting amt after t yrs
Ao = initial amt
h = half-life of substance
t = time
:
Using the half-life value of 2.44(10^5) yrs, initial amt as 1
1*2^(-t/2.44(10^5)) = .981 
using nat logs
{{{-t/(2.44(10^5))}}}*.693 = -.0192
:
{{{-t/(2.44(10^5))}}} = {{{(-.0192)/.693}}}
t = -2.44(10^5) * -.027675
:
t = +6753 ~ 7,000 yrs