If a substance has a half life of one million years, how much of its will be left after three million years? After four million years?
After 3 million years there will be 12.5% left. After 4 million, 6.25%.
The half-life of a substance is the amount of time it takes for half of that substance to decay. However, after two half-lives, half of the half remaining will decay, leaving you with one quarter of the original substance.
So, after 1 million years you will have 50% of the original substance remaining.
And, after 2 million years you will have 25% of the original substance remaining.
After 3 million years you will have 12.5% of the original substance remaining.
And after 4 million years you will have 6.25% of the original substance remaining.
You can generalize this to:
So for 0 half-lives, you have
One half-life gets you
For 3.323 half-lives:
Impact of this question
Creative Commons License