math(urgent)

Mary invested $30,000 in two accounts some at 12% per annum and the rest at 8% per annum. Her total interest for one years was $ 3200.How much was invested at each rate ?

solution :

$3200=P1 (0.12)(1)+ (3000-P1)(0.08)(1)

P1= ?

P2= 30000-P1 ?

HOW to solve this because they have two answer:

$20,000 at 12%
$10,000 at 8%

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asked by fizz
  1. well, of course they have two answers. They wanted to know the amount invested at each of two interest rates!

    So, what don't you understand? They gave you the equation. If P1 is invested at 12% (which is evident from the equation), then the rest of the money (30000-P1) was invested at 8%.

    Then just solve the equation for P1, and you get 20,000. The rest of the money (10,000) was invested at 8%.

    Now, if it's the mechanics of the equation, consider an equivalent one with less noise.

    2x + 3(10-x) = 22

    If you can do that, then you can do the one above.

    PS - I am not sure why they tossed in those (1) factors. Maybe because they want to explicitly note the amount of interest earned by 1 dollar.

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    posted by Steve

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