Question 442367
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20000$ is split into two investments one paying 5% and the other paying 6.5%. To the nearest cent how much should be 
invested in each so the yearly interest from the 5% investment is double the interest from 6.5% investment
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        The solution in the post by @mananth is incorrect due to arithmetic error.

        Below is my correct solution.



<pre>
let investment at  6.5%  be  x.
Investment at  5%  is  (20000-x).
...
0.05*x = 2*0.065*(20000-x)


Multiply by 100 both sides of the equation

    5x = 2*6.5(20000-x)

    5x = 260000 - 13x

    18x = 260000

    x = 260000/18 = 14,444.44 dollars invested at 6.5%.

    The rest, or 20,000 - 14,444.44 = 5,555.56 dollars invested at 5%.


<U>CHECK</U>.  The interest of the 5% investment is  14444.44*0.05 = 722.22.

        The interest of the 6.5% investment is  0.065*5555.56 = 361.11.

        The interest of the 5% investment is the doubled interest of the 6.5% investment.  ! correct !
</pre>

Solved correctly.