The half-life of 234U, uranium-234, 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?

Answer 1

(1/2)^(T/2.52*10^5) = 0.988

T is the time, in years, since it was 100% U-234.

Solve for T. Use of logs is recommended.

T = 4390 years

That rounds off to 4000 years.