Half-life is the time it takes for half of a sample of a radioactive element to decay. The function M(t)=P(1/2)^t/h can be used to calculate the mass remaining if the half-life is h and the initial mass is P. The half-life of radium is 1620 years.

a) How many years will it take until the laboratory has only 4 g of radium?

Question

Half-life is the time it takes for half of a sample of a radioactive element to decay. The function M(t)=P(1/2)^t/h can be used to calculate the mass remaining if the half-life is h and the initial mass is P. The half-life of radium is 1620 years. 

a) How many years will it take until the laboratory has only 4 g of radium?

anonymous · Answer

This is what I have so far:

M(t) = P(1/2)^t/1620
4 = 5(1/2)^t/1620
(1/2)^t/1620 = 4/5
log1/2(4/5)=t/1620
1620log1/2(4/5)=t

and then I'm stuck.......

anonymous · Answer

log1/2(4/5) = (log4/5)/(log1/2)