Protactinium-234 has a half life of 1.17 minutes. How long does it take for a 10 mg sample to decay to 2 mg?
We need to solve
Taking logs of both sides:
#(t/1.17) log(1/2) = log(1/5)#
#t/1.17 = (log(1/5))/(log(1/2)) = (-log(5))/(-log(2))#