The amount of material left after 2 half-lives is one half of the original amount true or false

It is false that the amount of material left after 2 half-lives is one half of the original amount.

Explanation:

The time taken by half of the nuclei to decay is called as half-life. Initially half of the nuclei are decayed in first half life and for the next half life again the half of remaining original nuclei decays.

In this way in the second half life the original material has fewer amounts than one of the original amount.

coal is not sustainable because it will one day run out.