R=3.7*10^10;//no. of alpha particles per second emitted by 1g of 226Ra//
N=(6.023*10^23)/226;//no. of atoms of 226Ra//
yr=3.15*10^7;//no of seconds in a year//
thalf=0.693*N/(R*yr);//half life of 226Ra in years//
printf('Half life of 226Ra molecule=t1/2=%fyears',thalf);//here the answer written in textbook is wrongly printed actual answer will be the one we are getting here//