Question 844689
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Hi,
Q(t) = {{{Q[0]e^(-kt ) }}}
first find k
 .5 = {{{e^(-k*1 ) }}}
 ln(.5)/-1 = k = .6931
25 = {{{100e^(-.6931t ) }}}
 .25 = {{{e^(-.6931t ) }}}
 {{{ln(.25)/(-.6931)}}} = t