Question 432653
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Hi
f(t)= 100(1/2)^t/5730 
If 20% of the carbon-14 remains, how old is the wood.
 .20 =(1/2)^t/5730 
 log.2/log.5 = t/5730
 5730(log.2/log.5) = t
 5730*2.3219 = 12,304.648  years old

make sense: 25% left after 2*5730 = 11,460 years