Q: A 50-g chunk of charcoal is found in the buried remains of an ancient city destroyed by invaders. The carbon-14 activity of the sample is 200 decays/min. Roughly when was the city destroyed? A: I used R = Ro*e^(-lambda*t) and t1/2 = ln2/lambda t1/2 = 3.834*10^-12 s-1 and 200 decays/min = 3.33 decays/sec or 3.33 Bq What is the initial acitivity/kg (Ro)? The final acitivty/kg = 3.33 Bq/0.05 Kg = 66.66 Bq/Kg Therefore R/Ro = 66.66/255 I then found the time to be 11 088 years Can someone please check over this and see if this looks correct and advise of any corrections? Many thanks!