Question

A sample of radioactive material has a half-life of 35 days. Calculate the fraction of the quantity that will remain after 105days

Answer 1

105 days is equal to 3 half-lives ($\frac{t}{t_{1/2}}=\frac{105}{35}=3$ ).

Assuming the initial quantity (N₀) of the material to be 1, the fraction equals:

$N=N_o(\frac{1}{2})^{\frac{t}{t_{1/2}}}=(\frac{1}{2})^3=0.125$

Answer: 0.125