Question

1. a substance has a half - life of 100,000 years. if the original amount is 50 grams, how much would there be after 2 half - lives (200,000 years)? 200 g 25 g 12.5 g 0 g

Explanation:

Step1: Calculate amount after first half - life

After one half - life, the amount is halved.
\(50\times\frac{1}{2}=25\) grams

Step2: Calculate amount after second half - life

After the second half - life, the amount is halved again.
\(25\times\frac{1}{2}=12.5\) grams

Answer:

12.5 g