A fossilized animal that was killed by a volcanic eruption has 6.25 percent of its original amount of carbon-14 remaining; this radioisotope has a half-life of 5730 years. How long ago did the volcano erupt?

a) 34,380 years agob) 22,920 years agoc) 17,190 years agod) 9,168 years ago

Respuesta :

With the assumption that the animal is 100kg the remaining mass is 6.25. (assumption of mass will not matter since the decrease in mass is in percentage.) 

To answer this we use the formula A=Aoe^-(ln2/t1/2)t
where 
A- final amount (6.25kg)
Ao - initial amount (100kg)
t1/2 - half life (5730)
t - time it takes to change A to Ao

plugging in the values 
t= 22920 years ago.Â