# Question #1991a

##### 1 Answer

#### Answer:

You'll be left with **6.0%** of the initial dose.

#### Explanation:

So, you know that potassium-42 has a nuclear half-life of **12.4 hours**. This means that the *initial dose* of potassium-42 gets **halved** every 12.4 hours.

Since the numbers don't allow for a quick calculation, you're going to have to use the nuclear hal-life equation

**(1)**, where

**t** hours;

The first thing you need to do is convert the time given to you from days to hours

This means that you get

To get the percentage of the initial dose that remains after **50.4 hours**, divide

Rounded to two sig figs, the answer will be