A fossilized animal that was killed by a volcano eruption has 12.5 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?
(Points : 3)

34,380 years ago

22,920 years ago

17,190 years ago

9,168 years ago

Question

A fossilized animal that was killed by a volcano eruption has 12.5 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?
 (Points : 3)  
       
34,380 years ago

        
22,920 years ago

        
17,190 years ago

        
9,168 years ago

anonymous · Answer

http://en.wikipedia.org/wiki/Half-life#Formulas_for_half-life_in_exponential_decay this might help :)

anonymous · Answer

The mass defect of a particular reaction resulted in the production of 5.50 x 1015 joules of energy. What mass (if totally converted to energy) would correspond to this amount of energy? (1 J = 1 kg m2/s2)
 (Points : 3)  
       
1.83 x 108 kg 

        
4.95 x 107 kg

        
6.11 x 10-2 kg

        
1.64 x 10-1 kg