algebra
posted by Anonymous on .
The halflife of 234U, uranium234, is 2.52 multiplied by 105 yr. If 98.8% of the uranium in the original sample is present, what length of time (to the nearest thousand years) has elapsed?

(1/2)^(T/2.52*10^5) = 0.988
T is the time, in years, since it was 100% U234.
Solve for T. Use of logs is recommended.
T = 4390 years
That rounds off to 4000 years.