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Assuming the age of the earth to be 10^(th) years , if the percentage of original amount of U^(238) still in existance on earth is x% (nearly) (t_(1//2) of U^(238) is 4.5 xx 10^(9) years) . Then 'x/10' is ____

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Solution :`LAMBDA t = 2.303 xx "log" ((N_(0))/(N_(t))) , (0.693)/(4.5 xx 10^(9)) xx 10^(10) = 2.303 xx log ((N_0)/(N_t)) , (3.010)/(4.5) = log ((N_0)/(N_t))`
`(10)/(15)= log ((N_0)/(N_t)) , log ((N_0)/(N_t)) = (2)/(3) , log ((N_0)/(N_t)) = 0.667, ((N_(0))/(N_(t))) `= anti log `(0.667) , ((N_0)/(N_t)) = (4.65)/(1)`
`((N_t)/(N_0)) = (1)/(4.65%) , % ((N_t)/(N_(0))) = (1)/(4.65) xx 100 = 21.5%` , Here `((X)/(10)) = (21.5%)/(10) = 2.15 -=2`


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