If 250 mg of a radioactive element decays to 200 mg in 48 hours, find the half-life of the element

Question

Help me solve this problem. 

Answer 1

200 = 250e^48k

0.8 = e^48k

ln 0.8 = 48k

-0.223 ≈ 48k

-0.0046 = k

 

0.5a = a₀e^(-0.004)t

0.5 = e^(-0.004)t

ln 0.5 = -0.004t

-0.693 ≈ -0.004t

173.25 ≈ t