A certain radioactive substance has a half-life of 5085 years. How long will it take for 75% of the substance to decay?

Q (t) .= amount of substance after t years. Let, Do be the initial amount at t=0. We know, equation modelling the radioactive decay is Q ( E ) = Q. e- Kt , where k is the radioactive decay constant. substance is We are given that half - life of 5085 years. that is after sofs years, amount of substance left is 2 Q ( 5085 ) = 2 = ) e - k ( 5085 ) = ) - 5085 k = In ( 3 )