After two half-lives, how much of the original material has decayed?
25 percent
50 percent
75 percent
100 percent
-
ET

75%

Explanation:

A half-life is the time taken to decay a radioactive material to half of its original weight.  

So if the original material was 100 then after 1 half life it would be half that: 50

Then after another half life it would be 25

So 75% of the original material has decayed.

75% of the material has decayed.

Explanation;

We can start this problem by solving the first half-life assuming the arbitrary condition stating that the initial concentration has a value of 100M, thus, for the first half-life, the concentration dwindles to 50M. Afterwards, the second half-life yields a concentration of 25M, meaning that the 75% of the material has decayed up to the second half-life, of course, the half of the result from the first half-life.

Hope this helps! :)

nucleic acid molecules are incredibly complex, containing the code that guarantees the four different nucleotide units comprise dna, the nucleic acid of interest to the genealogist. and one of four nitrogen-containing molecules called nucleotides