Afarmer in china discovers a mammal hide that contains 42% its original amount of c-14 (at time t=0) find the age of the mammal to the nearest year

Half-Life of Carbon-14 is 5,730 years
elapsed time = half-life * [log (bgng amt / end amt)] / log(2)
elapsed time = 5,730 * log (100 / 42) / log (2)
elapsed time = 5,730 * log  ( 2.380952381) / log(2)
elapsed time = 5,730 * 0.37675070961/ 0.30102999566
elapsed time = 7,171 years

Source:
http://www.1728.org/halflife.htm

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