What % of original radioactive atoms is left after 15 half lives ? a) 25 / 213 % b) 12.5 / 211 % c) 6.25 / 210 % d) 7.5 / 210 % Share with your friends Share 0 Sanjay Singh answered this Dear student Number of atoms lelt after n half life isN(t)=No2n (where No is the initial number of atoms and n is the number of half life)N(t)=No215Percentage of atoms left isN(t)No×100=1215×100=100215=100213×4=25213Regards 2 View Full Answer