[" 76.A sample of radioactive element has a mass of "82" .If kitial decay rate of a substance is "80" ,"],[10" gram at an instant t= "0" .The approximate "/" then after three.If half life of substance is "15" so "],[10" gram at an instant t= "0" .The approximate "],[" mass of this element in the sample after two mean three second the decay rate will be "],[" lives is :- "],[[" (1) "1.35" gram "," (2) "2.50" gram "],[[" (3) "3.70" gram "," (4) "6.30" gram "," (4) "100" disintegration/sec."]]]