A mixture of `Pu""^(239)` and `Pu""^(240)` has specific activity of `6xx10""^(9)`dps. The half lves of isotopes are `2.44xx10""^(4)` and `6.58xx10""^(3)`years respectively. The percent of `Pu""^(239)` in the mixture is x/10% (nearly). Then 'x' is

Answer

4

Explanation

`lamdaN" mix"=lamda""_(1)N""_(1)+lamda""_(2)N""_(2)`
`lamdaN" mix"=lamda""_(1)N""_(1)+lamda""_(2)(N-N""_(1))`
`lamda" mix"=(lamda""_(1)N""_(1))/N+lamda""_(2)-(lamda""_(2)N""_(1))/N`
`lamda " mix"-lamda""_(2)=(lamda""_(1)-lamda""_(2))N""_(1)/N""_(2),`
`N""_(1)/(N""_(2)=(lamda" mix"-lamda""_(2))/((lamda""_(1)-lamda""_(2))`