where Ao = starting amount, At = amount after time t, and k = rate constant
You are given that the half-life is 33 seconds
Calculate the rate constant
ln(2/1) = kx33 sec
0.693 = kx33
k = 0.0210 s^-1
Now calculate the amount left after 43.2 sec
ln(100%/A1%) = 0.0210 x 43.2
ln(100/A1) = 0.9074
100/A1 = 2.478
A1 = 40.4%
