Question 1023058
Let {{{ A }}} = amount in bank account 
after 1 yr
Let {{{ r }}} = interest rate needed
{{{ A = 2000 + r*2000 }}}
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The bank says {{{ A = 4000 }}} ( double {{{ 2000 }}} )
{{{ 4000 = 2000 + r*2000 }}}
{{{ r*2000 = 2000 }}}
{{{ r = 1 }}}
This is 100% interest rate