Uranium-235 has a half-life of 7.04 × 10⁸ years.How many years will it take for 99.9% of a U-235 sample to decay?

Name: Uranium-235 has a half-life of 7.04 × 10 8 years.How many years will it take for 99.9% of a U-235 sample to decay?
Brand: Quizplus
Rating: 4.8 (39 reviews)

Question

Quizplus · Accepted Answer

To decay 99.9%, 10 half-lives are needed (since 0.1% remains). 10 half-lives of U-235 is 7.04 × 10^8 years × 10 = 7.04 × 10^9 years, which is approximately 7.0 × 10^9 years.

Uranium-235 Has a Half-Life of 7