document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1133195>Question 1133195</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Walmart has a bike on sale for $150. The sign next to it says that the price is $25 off the original price. What is the original price? Define the variable and equation for the situation. Solve the equation.\r<BR>\n" );
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document.write( "This question is from my son's Math test. His answer is as follows:\r<BR>\n" );
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document.write( "Let x = original price<BR>\n" );
document.write( "x = 150 + 25; x = 175.\r<BR>\n" );
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document.write( "His teacher marked it wrong and wrote the equation as x - 25 = 150.\r<BR>\n" );
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document.write( "I don't see how the equation my son wrote is wrong? Could you please help me understand? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #750366 by </B><A HREF=/tutors/aboutme.mpl?userid=math_helper><B>math_helper(2461)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=math_helper><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/cgi-bin/show-face.mpl?user=math_helper><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=750366\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> x = 150 + 25 is equivalent to x - 25 = 150  (just add 25 to both sides to see this) <br>\r<BR>\n" );
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document.write( "I think his teacher is expecting to see the \"proper\" starting formulation of <BR>\n" );
document.write( "x - 25 = 150, which indeed makes a little more sense from the problem description.       \r<BR>\n" );
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document.write( "As an example, consider this simple age problem: <br><BR>\n" );
document.write( "John is 6 years younger than Alan<BR>\n" );
document.write( "Alan's age and John's age add to 70<BR>\n" );
document.write( "Find Alan's age<br>\r<BR>\n" );
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document.write( "Let Alan's age be x<BR>\n" );
document.write( "John's age is then: x - 6\r<BR>\n" );
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document.write( "As a teacher, I would expect the starting formulation to be:<BR>\n" );
document.write( "(x) + (x-6) = 70<br>\r<BR>\n" );
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document.write( "One wouldn't expect the student, instead, to create a starting formulation of:<br>  2x = 76 <br>  even though they are equivalent.\r<BR>\n" );
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document.write( "Just to follow up:  I used \"proper\" loosely to mean \"most representative of the problem described.\"   As tutor Boreal said, it is easy to make a mistake if one starts solving the problem in their head.  <br>  \r<BR>\n" );
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document.write( "You know the starting point should be x-25=150 because the problem asks for the original price and it says \"$25 off the original\"  (off ==> subtraction).  <br>\r<BR>\n" );
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document.write( "Basically your son partly solved the equation \"x-25=150\" in his head to arrive at the equivalent \"x=150+25\"  which will be error-prone for more complex problems.   \r<BR>\n" );
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document.write( " </SPAN>\n" );
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