document.write( "Question 1099909: Jack inherited 250,000 pesos and invested money in SM, Meralco, and Manila Water. After a year, he got a small return of 16,200 pesos from the three investments. SM returned 6%, Meralco returned 7%, and Manila Water returned 8%. There was 60,000 more invested in Meralco than in Manila Water. How much did he invest in SM, Meralco, and Manila Water? \n" ); document.write( "
Algebra.Com's Answer #714413 by richwmiller(17219)\"\" \"About 
You can put this solution on YOUR website!
.06x+.07y+.08z=16200
\n" ); document.write( "x+y+z=250000
\n" ); document.write( "0x+y-z=60000\r
\n" ); document.write( "\n" ); document.write( ".06,.07,.08,16200
\n" ); document.write( "1,1,1,250000
\n" ); document.write( "0,1,-1,60000\r
\n" ); document.write( "\n" ); document.write( "SM=150000, Meralco=80000, Manila Water=20000
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Solved by pluggable solver: Using Cramer's Rule to Solve Systems with 3 variables

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\n" ); document.write( " First let \"A=%28matrix%283%2C3%2C0.06%2C0.07%2C0.08%2C1%2C1%2C1%2C0%2C1%2C-1%29%29\". This is the matrix formed by the coefficients of the given system of equations.
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\n" ); document.write( " Take note that the right hand values of the system are \"16200\", \"250000\", and \"60000\" and they are highlighted here:
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\n" ); document.write( " These values are important as they will be used to replace the columns of the matrix A.
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\n" ); document.write( " Now let's calculate the the determinant of the matrix A to get \"abs%28A%29=0.03\". To save space, I'm not showing the calculations for the determinant. However, if you need help with calculating the determinant of the matrix A, check out this solver.
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\n" ); document.write( " Notation note: \"abs%28A%29\" denotes the determinant of the matrix A.
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\n" ); document.write( " Now replace the first column of A (that corresponds to the variable 'x') with the values that form the right hand side of the system of equations. We will denote this new matrix \"A%5Bx%5D\" (since we're replacing the 'x' column so to speak).
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\n" ); document.write( " Now compute the determinant of \"A%5Bx%5D\" to get \"abs%28A%5Bx%5D%29=4500\". Again, as a space saver, I didn't include the calculations of the determinant. Check out this solver to see how to find this determinant.
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\n" ); document.write( " To find the first solution, simply divide the determinant of \"A%5Bx%5D\" by the determinant of \"A\" to get: \"x=%28abs%28A%5Bx%5D%29%29%2F%28abs%28A%29%29=%284500%29%2F%280.03%29=150000\"
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\n" ); document.write( " So the first solution is \"x=150000\"
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\n" ); document.write( " We'll follow the same basic idea to find the other two solutions. Let's reset by letting \"A=%28matrix%283%2C3%2C0.06%2C0.07%2C0.08%2C1%2C1%2C1%2C0%2C1%2C-1%29%29\" again (this is the coefficient matrix).
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\n" ); document.write( " Now replace the second column of A (that corresponds to the variable 'y') with the values that form the right hand side of the system of equations. We will denote this new matrix \"A%5By%5D\" (since we're replacing the 'y' column in a way).
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\n" ); document.write( " Now compute the determinant of \"A%5By%5D\" to get \"abs%28A%5By%5D%29=2400\".
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\n" ); document.write( " To find the second solution, divide the determinant of \"A%5By%5D\" by the determinant of \"A\" to get: \"y=%28abs%28A%5By%5D%29%29%2F%28abs%28A%29%29=%282400%29%2F%280.03%29=80000\"
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\n" ); document.write( " So the second solution is \"y=80000\"
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\n" ); document.write( " Let's reset again by letting \"A=%28matrix%283%2C3%2C0.06%2C0.07%2C0.08%2C1%2C1%2C1%2C0%2C1%2C-1%29%29\" which is the coefficient matrix.
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\n" ); document.write( " Replace the third column of A (that corresponds to the variable 'z') with the values that form the right hand side of the system of equations. We will denote this new matrix \"A%5Bz%5D\"
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\n" ); document.write( " Now compute the determinant of \"A%5Bz%5D\" to get \"abs%28A%5Bz%5D%29=600\".
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\n" ); document.write( " To find the third solution, divide the determinant of \"A%5Bz%5D\" by the determinant of \"A\" to get: \"z=%28abs%28A%5Bz%5D%29%29%2F%28abs%28A%29%29=%28600%29%2F%280.03%29=20000\"
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\n" ); document.write( " So the third solution is \"z=20000\"
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\n" ); document.write( " Final Answer:
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\n" ); document.write( " So the three solutions are \"x=150000\", \"y=80000\", and \"z=20000\" giving the ordered triple (150000, 80000, 20000)
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\n" ); document.write( " Note: there is a lot of work that is hidden in finding the determinants. Take a look at this 3x3 Determinant Solver to see how to get each determinant.
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\n" ); document.write( "\n" ); document.write( "gauss jordan
\n" ); document.write( "same as elimination without the variables
\n" ); document.write( ".06x+.07y+.08z=16200
\n" ); document.write( "x+y+z=250000
\n" ); document.write( "0x+y-z=60000
\n" ); document.write( "original 3*4 matrix
\n" ); document.write( "0.06,0.07,0.08,16200
\n" ); document.write( "1,1,1,250000
\n" ); document.write( "0,1,-1,60000\r
\n" ); document.write( "\n" ); document.write( "divide row 1 by 0.06
\n" ); document.write( "1,1.16666667,1.33333333,270000
\n" ); document.write( "1,1,1,250000
\n" ); document.write( "0,1,-1,60000\r
\n" ); document.write( "\n" ); document.write( "add -1*row 1 to row 2
\n" ); document.write( "1,1.16666667,1.33333333,270000
\n" ); document.write( "0,-0.16666667,-0.33333333,-20000
\n" ); document.write( "0,1,-1,60000\r
\n" ); document.write( "\n" ); document.write( "add 0*row 1 to row 3
\n" ); document.write( "1,1.16666667,1.33333333,270000
\n" ); document.write( "0,-0.16666667,-0.33333333,-20000
\n" ); document.write( "0,1,-1,60000\r
\n" ); document.write( "\n" ); document.write( "divide row 2 by -0.16666667
\n" ); document.write( "1,1.16666667,1.33333333,270000
\n" ); document.write( "0,1,2.0,120000.0
\n" ); document.write( "0,1,-1,60000\r
\n" ); document.write( "\n" ); document.write( "add -1*row 2 to row 3
\n" ); document.write( "1,1.16666667,1.33333333,270000
\n" ); document.write( "0,1,2.0,120000.0
\n" ); document.write( "0,0,-3.0,-60000.0\r
\n" ); document.write( "\n" ); document.write( "divide row 3 by -3.0
\n" ); document.write( "1,1.16666667,1.33333333,270000
\n" ); document.write( "0,1,2.0,120000.0
\n" ); document.write( "0,0,1,20000.0\r
\n" ); document.write( "\n" ); document.write( "add -2.0*row 3 to row 2
\n" ); document.write( "1,1.16666667,1.33333333,270000
\n" ); document.write( "0,1,0,80000.0
\n" ); document.write( "0,0,1,20000.0\r
\n" ); document.write( "\n" ); document.write( "add -1.33333333*row 3 to row 1
\n" ); document.write( "1,1.16666667,0,243333.333
\n" ); document.write( "0,1,0,80000.0
\n" ); document.write( "0,0,1,20000.0\r
\n" ); document.write( "\n" ); document.write( "add -1.16666667*row 2 to row 1
\n" ); document.write( "1,0,0,150000.0
\n" ); document.write( "0,1,0,80000.0
\n" ); document.write( "0,0,1,20000.0\r
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\n" ); document.write( "\n" ); document.write( "1 150000.0
\n" ); document.write( "2 80000.0
\n" ); document.write( "3 20000.0
\n" ); document.write( "done
\n" ); document.write( "check
\n" ); document.write( ".06*150000+.07*80000+.08*20000=16200
\n" ); document.write( "9000+5600+1600=16200
\n" ); document.write( "16200=16200
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