1. The problem statement, all variables and given/known data A sample of sodium pertechnetate injection was found to have an activity of 51439 counts per minute (cpm). The sample was measured again exactly after 8 hours and found to have an activity of 20476 cpm. Calculate the half life of sodium pertechnatate. 2. Relevant equations A = A0 e^-lamdat ln A = in A0 - lamdat half life = ln2/lamda 3. The attempt at a solution ln 20476 = ln 51439 -lamda * 8 9.927008748 = 10.84815192 - lamda * 8 0.9150875487/8 = -lamda lamda = 0.1143859436 half life = 6.06 hours Is this correct? I think I did the algebra a bit wrong but the answer of 6 hours sounds about right... can anyone help please...thanks.