Physics - Modern Physics Question with Solution | TestHub

In first$2 \mathrm{s}$, number of nucleons present is$900$out of$1000$,
This means Percentage number of nuclei left$=\frac{900}{1000}\times 100=90\mathrm{\%}$, i.e.,$90\mathrm{\%}$nuclei are left behind.
Therefore in next$2 \mathrm{s}$,$90\mathrm{\%}$of$900$nuclei will be left.
Number of nuclei left$=\frac{90}{100}\times 900=810$, i.e.,$810$nuclei will be left.