An unknown radioactive element decays into non-radioactive substances. In 240 days the radioactivity of a sample decreases by 45 percent.

(a) What is the half-life of the element?
in (days)

(b) How long will it take for a sample of 100mg to decay to 58 mg?
in (days)

Question

An unknown radioactive element decays into non-radioactive substances. In 240 days the radioactivity of a sample decreases by 45 percent.

(a) What is the half-life of the element?
 in (days)

(b) How long will it take for a sample of 100mg to decay to 58 mg? 
in (days)

anonymous · Answer

i dont know how to use the y=Ce^kt equation to solve for this problem. Help!!