Question 1039797
Let {{{ V }}} = the current value of the coin
{{{ V = 20*( 1 + .035 )^15 }}}
{{{ V = 20*1.035^15 }}}
{{{ V = 20*1.6753 }}}
{{{ V = 33.507 }}}
The coin will be worth $33.51 in 15 yrs
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Double the value of the coin is {{{ 2*20 = 40 }}}
Let {{{ t }}} = time in years when coin is worth $40
{{{ 40 = 20*1.035^t }}}
{{{ 2 = 1.035^t }}}
Take the log of both sides
{{{ log(2) = t*log( 1.035 ) }}}
{{{ .30103 = .01494t }}}
{{{ t = .30103/.01494 }}}
{{{ t = 20.1488 }}}
The coin will double in value in the 20th year