Physics

Problem

Two pure radioactive isotopes A and B each contain the same number of nuclei at

t=0

. The half-life of A is

2\,\text{days}

, while that of B is

5\,\text{days}

. Calculate, to two significant figures, the ratio of their activities

\dfrac{A_A}{A_B}

after

4\,\text{days}

. a) 5.7 b) 0.44 c) 1.1 d) 2.5