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## Homework Statement

The half-life of a radioactive substance is 194 days. How many days will it take for 80% of the substance to decay?

## Homework Equations

## The Attempt at a Solution

I had to make 1/2

^{n}=1/5. I did this by finding log

_{2}5=n. After this, I needed to only multiply by the number of days it took the half-life to occur, which was 194, and got 451 (approx.) as a reasonable answer.

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