Question 1055032
{{{ 5 = 15*e^( -.244t ) }}}
{{{ 1/3 = e^(-.244t ) }}}
Take the natural log of both sides
{{{ ln(1/3) = ln( e^(-.244t )) }}}
{{{ -1.0986123 = -.244t }}}
{{{ t = 4.5025 }}}
It will take 4.50 yrs
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check:
{{{ 5 = 15*e^( -.244t ) }}}
{{{ 5 = 15*e^( -.244*4.5025 ) }}}
{{{ 5 = 15*e^( -1.09861 ) }}}
{{{ 5 = 15*.333334 }}}
{{{ 5 = 5.00001 }}}
close enough