<u>Answer:</u> The amount of sample left after 20 years is 288.522 g and after 50 years is 144.26 g
<u>Explanation:</u>
We are given a function that calculates the amount of sample remaining after 't' years, which is:

Putting values in above equation:


Hence, the amount of sample left after 20 years is 288.522 g
Putting values in above equation:


Hence, the amount of sample left after 50 years is 144.26 g
The number of hours required : 37.2 hours
<h3>Further explanation</h3>
Given
⁴²K (potassium -42)
Required
The number of hours
Solution
The atomic nucleus can experience decay into 2 particles or more due to the instability of its atomic nucleus.
Usually, radioactive elements have an unstable atomic nucleus.
Based on Table N(attached), the half-life for ⁴²K is 12.4 hours, which means half of a sample of ⁴²K will decay in 12.4 hours
For three half-life periods :

Force is a strength or energy as an attribute or physical action or movement, motion is the action or process of moving or being moved
Acceleration is the rate of change and is constantly positive
The answers for Acceleration:
m/s^2
Change in velocity over change in time
Velocity is the speed of the object but also involves direction can be both negative and positive
The answers for Velocity:
m/s
Can be positive or negative
Change in displacement over change in time
Both Acceleration and Velocity:
A rate of change