A parent nuclide X decays to radioactive daughter Y

PHYSICS · Subjective · CBSE · Physics · Nuclei · Nuclei

Problem

A parent nuclide X decays to radioactive daughter Y, which subsequently decays to a stable product. The half-lives are

t_{1/2,X}=15\,\text{d}

and

t_{1/2,Y}=3.0\,\text{d}

. At

t=0

only X is present. Determine the time, in days, at which the activity of Y equals the activity of X.