Annual simple interest

Question

If $2000 is invested at 10% simple natural interest, how much should be invested at 12% annual simple interest so that the total yearly income for both investments is $5000?

Answer 1

$2,000 * 110%  +  x * 112%  =  $5,000

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$2,000 * 1.10    +  x * 1.12    =  $5,000

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      $2,200        +   1.12 x      =  $5,000

    - $2,200                               - $2,200

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                             1.12 x      =  $2,800

                           / 1.12           /  1.12

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                                    x       =  $2,500