SOLUTION: 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 intrest from the 5% investment is

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Question 442367: 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 intrest from the 5% investment is double the intrest from 6.5% investment
Found 3 solutions by mananth, ikleyn, timofer:
Answer by mananth(16949) About Me  (Show Source):
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let investment at 6.5% be x
Investment at 5 % = (20000-x)
...
5%x= 2*6.5%(20000-x)
multiply by 100
5x=2*6.5(20000-x)
5x=130000-13x
18x=130000
x= 7,222.22 at6. 5%
Balance at 6.5%

Answer by ikleyn(53427) About Me  (Show Source):
You can put this solution on YOUR website!
.
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. 


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%.


CHECK.  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 !

Solved correctly.



Answer by timofer(136) About Me  (Show Source):
You can put this solution on YOUR website!
6.5% part
0.065x

5% part
0.05%2820000-x%29

The interest from the 5% is to be double the interest at 6.5%.
%280.05%2820000-x%29%29%2F%280.065x%29=2

%2850%2820000-x%29%29%2F%2865x%29=2

%2810%2820000-x%29%29%2F%2813x%29=2

5%2820000-x%29=13x

100000-5x=13x

100000=18x

x=5555.56 at 6.5%
14444.44 at 5%