A radioactive substance decays at a rate of 8% per year. If the initial mass is 200 grams, what will be the mass after 5 years? - Redraw

Understanding the Context

The Growing Conversation Around Radioactive Decay in the U.S.

Radioactive decay is increasingly relevant in modern life, from cancer treatment using targeted radiation to tracking contaminants in food and water. As more people engage with health informatics and scientific literacy, topics like decay rates are gaining traction—especially when people seek reliable, evidence-based answers. The steady, annual 8% loss reflects not only physics principles but also a broader public interest in understanding longevity of materials in safe, natural ways.

The Science Behind the 8% Annual Decay Rate

Key Insights

Radioactive decay is scientifically defined by a half-life—the time it takes for half the material to transform. While not every substance decays like carbon-14, many isotopes operate on similar exponential decay patterns. With an 8% annual decay rate, the material loses a consistent fraction each year, creating a predictable decline. At 200 grams, this results in clear measurable reduction over five years—ideal for those tracking material lifespan in labs, healthcare, or environmental studies.

To calculate the mass after 5 years, apply a straightforward formula:
Remaining mass = Initial mass × (1 – decay rate)^number of years
So: 200 × (1 – 0.08)^5 = 200 × (0.92)^5 ≈ 200 × 0.659 = 131.8 grams

The gradual loss reflects the steady breakdown without sudden transformation—making it reliable for modeling decay in controlled environments.

How Radioactive Decay at 8% Per Year Works in Practice

Final Thoughts

The process unfolds as each year’s loss is based on the remaining mass, not an absolute amount. Year one reduces 200 grams to 184 grams, continuing so each year a smaller proportional chunk vanishes. Over five years, this compounding effect yields a