SOLUTION: Last year, Charlie had $20,000 to invest. He invested some of it in an account that paid 10% simple interest per year, and he invested the rest in an account that paid 7%

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Question 927560: Last year, Charlie had
$20,000
to invest. He invested some of it in an account that paid
10%
simple interest per year, and he invested the rest in an account that paid
7%
simple interest per year. After one year, he received a total of
$1640
in interest. How much did he invest in each account?
Answer by srinivas.g(540)   (Show Source): You can put this solution on YOUR website!
Let x be the amount invested in an account that paid 10 % per year
Let y be the amount invested in an account that paid 7 % per year
x+y= $ 20,000.......................eq(1)
interest on amount = 10 % of X
=
=
=
Interest on amount y = 7 % of y
=
=
Total interest for whole amount = $ 1640
hence
0.1 x+0.07 y =1640.............eq(2)
solve eq(1) and eq(2) to get x& Y values
Solved by pluggable solver: SOLVE linear system by SUBSTITUTION
Solve:
We'll use substitution. After moving 1*y to the right, we get:
, or . Substitute that
into another equation:
and simplify: So, we know that y=12000. Since , x=8000.

Answer: .
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