0.9^18

For the perfectionist, it is a warning: repetition magnifies small flaws. For the survivalist, it is a comfort: even a slow decline takes a significant amount of time to reach total depletion.

We can compute stepwise:

If a population of endangered animals, a financial investment, or a radioactive isotope retains $90%$ of its value year after year, it is decaying very slowly. But how long does it take to lose the vast majority of the starting amount? 0.9^18

In the world of mathematics, simple numbers often hide profound truths. At first glance, the expression looks like a straightforward arithmetic problem. It involves a number very close to one, raised to a modest power. For the perfectionist, it is a warning: repetition

However, the equation $0.9^{18}$ represents a chain of dependency. It asks: What happens if that process is repeated 18 times? But how long does it take to lose

Probability of succeeding at least once = 1 - (0.1)^18 ≈ 1 - 0