# Radioactive Decay: Understanding Potassium-40 Half-Life

## What percentage of potassium-40 remains from a creature that died 500 million years ago?

Based on the data, how much potassium-40 is still present after 500 million years since the creature's death?

## Answer:

Approximately 79% of the original potassium-40 remains after 500 million years.

Potassium-40, a radioactive isotope, has a half-life of 1.25 billion years. This means that it takes 1.25 billion years for half of the atoms in a sample of potassium-40 to decay.

Given that the creature died 500 million years ago, which is less than one half-life of potassium-40, we can deduce that more than half of the original potassium-40 still remains. In fact, calculations show that approximately 79% of the initial amount of potassium-40 is still present.

To calculate the exact amount remaining, the formula N = N0 (1/2)^(t/T) is used, where N is the final amount, N0 is the initial amount, t is the time elapsed, and T is the half-life. By plugging in the values, we arrive at the result that about 79% of the original potassium-40 remains after 500 million years.

Understanding radioactive decay and half-life is crucial in various scientific fields, including archaeology, geology, and biology. It allows scientists to determine the age of rocks, fossils, and artifacts, providing valuable insights into the Earth's history.