a radioactive isotope X of half life of 1.37 X 10^ 9 yrs decays to Y which is stable. a sample of rocks frm moon ws found to contain both X & Y in the ratio 1:7 . the age of rock is ? ans is 4.11 X 10^ 9 yrs .hw?
thus t=3x1.37x10^9 yrs=4.11x10^9