document.write( "Question 126566: A certain 18 hole golf course has par-3 par-4 and par-5 hole and there are twice as many par-4 holes as there are par-5. How many holes of each type are there if a golfer has par on every hle for a score of 70? \n" ); document.write( "
Algebra.Com's Answer #92721 by marcsam823(57)\"\" \"About 
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Let x = number of par-3 holes
\n" ); document.write( "Let y = number of par-4 holes
\n" ); document.write( "Let z = number of par-5 holes
\n" ); document.write( "Let \"x+%2B+y+%2B+z+=+18\" (total number of holes on the course)
\n" ); document.write( "Let 3x = total number of strokes for par-3 holes
\n" ); document.write( "Let 4y = total number of strokes for par-4 holes
\n" ); document.write( "Let 5z = total number of strokes for par-5 holes
\n" ); document.write( "Let \"3x+%2B+4y+%2B+5z+=+70\" (total strokes to par the course)
\n" ); document.write( "Let \"y+=+2z\" (number of par-4 holes = twice the number of par-5 holes)\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "1. We'll start by reducing the number of variables from 3 to 2
\n" ); document.write( "Equation 1: \"x+%2B+y+%2B+z+=+18\"
\n" ); document.write( "Equation 2: \"3x+%2B+4y+%2B+5z+=+70\"
\n" ); document.write( "We know that \"y+=+2z\" (from above) so let's substitute for y:
\n" ); document.write( "Equation 1:
\n" ); document.write( "\"x+%2B+2z+%2B+z+=+18\"
\n" ); document.write( "\"x+%2B+3z+=+18\"
\n" ); document.write( "Equation 2:
\n" ); document.write( "\"3x+%2B+4%282z%29+%2B+5z+=+70\"
\n" ); document.write( "\"3x+%2B+8z+%2B+5z+=+70\"
\n" ); document.write( "\"3x+%2B+13z+=+70\"\r
\n" ); document.write( "\n" ); document.write( "Now we have two equations with 2 variables each:
\n" ); document.write( "Equation 1 is now: \"x+%2B+3z+=+18\"
\n" ); document.write( "and
\n" ); document.write( "Equation 2 is now: \"3x+%2B+13z+=+70\"\r
\n" ); document.write( "\n" ); document.write( "We can solve for z by eliminating the x variable:
\n" ); document.write( "Multiply both sides of Equation 1 by -3:
\n" ); document.write( "\"-3%28x+%2B+3z%29+=+-3%2818%29\"
\n" ); document.write( "\"-3x+-9z+=+-54\"
\n" ); document.write( "Add this to Equation 2 and solve for z:
\n" ); document.write( " \"3x+%2B+13z+=+70\"
\n" ); document.write( "+ \"-3x+-9z+=+-54\"
\n" ); document.write( "\"4z+=+16\"
\n" ); document.write( "\"z+=+4\"
\n" ); document.write( "Solve for x and y:
\n" ); document.write( "We know that y = 2z
\n" ); document.write( "\"y+=+2%284%29\"
\n" ); document.write( "\"y+=+8\"
\n" ); document.write( "We also know that x + y + z = 18
\n" ); document.write( "\"x+%2B+8+%2B+4+=+18\"
\n" ); document.write( "\"x+%2B+12+=+18\"
\n" ); document.write( "\"x+=+6\"
\n" ); document.write( "The golf course has 6 par-3 holes, 8 par-4 holes and 4 par-5 holes\r
\n" ); document.write( "\n" ); document.write( "Check:
\n" ); document.write( "Let's test these results with the original equation 2:
\n" ); document.write( "\"3x+%2B+4y+%2B+5z+=+70\"
\n" ); document.write( "\"3%286%29+%2B+4%288%29+%2B+5%284%29=+70\"
\n" ); document.write( "\"18+%2B+32+%2B+20+=+70\"
\n" ); document.write( "\"70+=+70\"
\n" ); document.write( "This checks. Our answers are correct.
\n" ); document.write( "18 + 32 + 20 = 70\r
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