document.write( "Question 927560: Last year, Charlie had
\n" ); document.write( "$20,000
\n" ); document.write( " to invest. He invested some of it in an account that paid
\n" ); document.write( "10%
\n" ); document.write( " simple interest per year, and he invested the rest in an account that paid
\n" ); document.write( "7%
\n" ); document.write( " simple interest per year. After one year, he received a total of
\n" ); document.write( "$1640
\n" ); document.write( " in interest. How much did he invest in each account? \n" ); document.write( "
Algebra.Com's Answer #563062 by srinivas.g(540)\"\" \"About 
You can put this solution on YOUR website!
Let x be the amount invested in an account that paid 10 % per year
\n" ); document.write( " Let y be the amount invested in an account that paid 7 % per year
\n" ); document.write( " x+y= $ 20,000.......................eq(1)
\n" ); document.write( "interest on amount = 10 % of X
\n" ); document.write( " =\"+%2810%2F100%298x\"
\n" ); document.write( " =\"%281%2F10%29%2Ax\"
\n" ); document.write( " =\"0.1x\"
\n" ); document.write( "Interest on amount y = 7 % of y
\n" ); document.write( " = \"+%287%2F100%29%2Ay\"
\n" ); document.write( " =\"0.07y\"
\n" ); document.write( "Total interest for whole amount = $ 1640
\n" ); document.write( "hence
\n" ); document.write( " 0.1 x+0.07 y =1640.............eq(2)
\n" ); document.write( "solve eq(1) and eq(2) to get x& Y values
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Solved by pluggable solver: SOLVE linear system by SUBSTITUTION
Solve:
\n" ); document.write( " We'll use substitution. After moving 1*y to the right, we get:
\n" ); document.write( " \"1%2Ax+=+20000+-+1%2Ay\", or \"x+=+20000%2F1+-+1%2Ay%2F1\". Substitute that
\n" ); document.write( " into another equation:
\n" ); document.write( " \"0.1%2A%2820000%2F1+-+1%2Ay%2F1%29+%2B+0.07%5Cy+=+1640\" and simplify: So, we know that y=12000. Since \"x+=+20000%2F1+-+1%2Ay%2F1\", x=8000.
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\n" ); document.write( " Answer: \"system%28+x=8000%2C+y=12000+%29\".
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