document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=786666>Question 786666</A>: <I><SPAN STYLE=\"word-break: break-all;\"> Suppose you invest $4,900 in stocks and bonds paying 7% and 3%, respectively. The interest from both investments after one year is $239. For the following problems, use x for the amount invested in stocks and y for the amount invested in bonds.\r<BR>\n" );
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document.write( "Write a mathematical expression for the total amount of money invested<BR>\n" );
document.write( "I put 07y+.03x+239=4900 but it was wrong </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #477938 by </B><A HREF=/tutors/aboutme.mpl?userid=DrBeeee><B>DrBeeee(684)</B></A><img src=\"/images/stars/stars-11.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=DrBeeee><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/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=477938\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> Sorry but it is wrong.<BR>\n" );
document.write( "Let x = amount invested in stock paying 7%<BR>\n" );
document.write( "Let y = amount invested in bonds paying 3%<BR>\n" );
document.write( "The answer to \"Write a mathematical expression for the total amount of money invested\" is simply<BR>\n" );
document.write( "(1) x + y<BR>\n" );
document.write( "However, if the real question is to find out the amount of x and y, we need two equations, the total invested given by<BR>\n" );
document.write( "(2) x + y = 4900 and the interest earned after one year given by<BR>\n" );
document.write( "(3) 0.07x + 0.03y = 239<BR>\n" );
document.write( "We must solve the system of equations given by (2) and (3).<BR>\n" );
document.write( "I don't like to use decimals so I multiply both sides of (3) by 100 to get<BR>\n" );
document.write( "(4) 7x + 3y = 23900<BR>\n" );
document.write( "Now substitute<BR>\n" );
document.write( "(5) x = 4900 - y from (2) into (4) to get<BR>\n" );
document.write( "(6) 7*(4900 - y) + 3y = 23900 or<BR>\n" );
document.write( "(7) 34300 - 7y + 3y = 23900 or <BR>\n" );
document.write( "(8) 34300 - 4y = 23900 or <BR>\n" );
document.write( "(9) -4y = 23900 - 34300 or<BR>\n" );
document.write( "(10) 4y = 10400 or <BR>\n" );
document.write( "(11) y = 10400/4 or<BR>\n" );
document.write( "(12) y = 2600<BR>\n" );
document.write( "And from (2) we get<BR>\n" );
document.write( "(13) x = 4900 - 2600 or<BR>\n" );
document.write( "(14) x = 2300<BR>\n" );
document.write( "Let's check this with (3).<BR>\n" );
document.write( "Is (0.07*2300 + 0.03*2600 = 239)?<BR>\n" );
document.write( "Is (161 + 78 = 239)?<BR>\n" );
document.write( "Is (239 = 239)? Yes<BR>\n" );
document.write( "Answer to (possible) question: you invested $2300 in stock and $2600 in bonds.\r<BR>\n" );
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document.write( " <BR>\n" );
document.write( " </SPAN>\n" );
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