Question 1108964
{{{ A(t) = 4000*e^( .04t ) }}}
After {{{ t }}} years, the investment triples
{{{ A(t) = 3*4000 }}}
{{{ A(t) = 12000 }}}
{{{ 12000 = 4000*e^( .04t ) }}}
{{{ 3 = e^( .04t ) }}}
Take the natural log of both sides
{{{ ln(3) = .04t }}} ( they may just want this )
{{{ 1.0986 = .04t }}}
{{{ t = 1.0986 / .04 }}}
{{{ t = 27.4653 } }}} yrs