We can calculate the age by using the formula: final amount=initial amount*(1/2)^(time/half-life), or t=ln(final amount/initial amount)/(-0.693)*half-life. The half life of C-14 is 5730 years, and final amount=initial amount is 71% or 0.71, so t=ln(0.71)/(-0.693)*5730=2832 years approximately.
