Half life is the period of time it takes for one-half of the atoms of an original isotope to decay.
[tex]formula=(\frac{1}{2})^{n}[/tex]
In this example we have: [tex](\frac{1.25 kg}{10kg})^{n}[/tex] where n= the number of half lives.
Thus: [tex]\frac{1.25kg}{10kg} =\frac{1}{8}[/tex]
[tex]\frac{1}{8} =(\frac{1}{2})^{n}[/tex] From this equation n=3. The answer to your question is: 3 half lives have passed which gives the meteorite an age of 4.5*3= 13.5 billion years.
