1. The problem statement, all variables and given/known data I need to write a program that, given the decay constant of a radioactive material, will calculate numerically (to withing one second) the time taken for half of the orginal sample of material to decay. 2. Relevant equations λ = decay constant C0 = start amount of material After one second C0 will have decayed leaving C = (1-λ)C0 of undecayed material left. 3. The attempt at a solution I only have very basic experince at programming so I am finding this quite difficult. Below is the code that I have created so far. IMPlICIT NONE REAL :: y,C,t !y = decay constant C = starting amount of material t = time PRINT*,"Enter decay constant" READ*,y PRINT*,"Enter starting amount of material" READ*,C DO WHILE (C.GT.C/2) C=(1-y)*C END DO PRINT*,"C=",C I don't really have any idea how I would work out hiw many interations the DO WHILE loop has done which i need to kno in order to work out the half life. Any help/advice would be much appreciated.