document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1161827>Question 1161827</A>: <I><SPAN STYLE=\"word-break: break-all;\"> In a tropical fish store, one tank contains 65 kilograms of seawater with 7% salt.<BR>\n" );
document.write( "a. How much pure water must be added to have 5% salt?<BR>\n" );
document.write( "b. How much water must be evaporated to contain 9% salt? </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #785458 by </B><A HREF=/tutors/aboutme.mpl?userid=Theo><B>Theo(13342)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=Theo><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=Theo><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=785458\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> you start with 65 kilograms of seawater that is 7% salt.<BR>\n" );
document.write( "that means that 7% of the seawater is salt and 93% of the seawater is pure water.<BR>\n" );
document.write( "that means you have 4.55 kilograms of salt and 60.45 kilograms of pure water.\r<BR>\n" );
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document.write( "if you want to get 5% seawater, you have to add pure water.<BR>\n" );
document.write( "if you want to get 9% seawater, you have to add salt.\r<BR>\n" );
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document.write( "we'll use the variable called x to determine the amount of pure water to add to get 5% seawater and then we'll use the variable called x to determine the amount of salt to add to get 9% seawater.\r<BR>\n" );
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document.write( "if you want 5% seawater, than you have to have 95% pure water.<BR>\n" );
document.write( "your first equation is therefore:<BR>\n" );
document.write( ".95 * (65 + x) = 60.45 + x<BR>\n" );
document.write( "solve this equation and you will get x = 26 kilograms.<BR>\n" );
document.write( "60.45 + 26 = 86.45 kilograms of pure water.<BR>\n" );
document.write( "add 4.55 kilograms of salt (you didn't add any more salt to the mixture, only pure water) to get 91 kilograms of seawater.<BR>\n" );
document.write( "86.45 / 91 = .95 = 95% pure water.<BR>\n" );
document.write( "that means 5% salt which is what you want.\r<BR>\n" );
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document.write( "if you want 9% salt, then your second equation becomes:<BR>\n" );
document.write( ".09 * (65 + x) = 4.55 + x<BR>\n" );
document.write( "solve this equation and you will get x = 1.428571429 kilograms.<BR>\n" );
document.write( "4.55 + x = 5.978571q429 kilograms of salt.<BR>\n" );
document.write( "add 60.45 kilograms of water (you didn't add any pure water to the mixture, only salt) to get 65.97857143 kilograms of seawater.<BR>\n" );
document.write( "4.978571429 / 65.97857143 = .09 = 9% salt.\r<BR>\n" );
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document.write( "your solutions are therefore.<BR>\n" );
document.write( "add 26 kilograms of pure water to 65 kilograms of seawater that is 7% salt to get 91 kilograms of seawater that is 5% salt.<BR>\n" );
document.write( "add 1.428571429 kilograms of salt to 65 kilograms of seawater that is 7% salt to get 65.97857143 kilograms of seawater that is 9% salt.\r<BR>\n" );
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document.write( "HOWEVER, .....\r<BR>\n" );
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document.write( "you were not asked to add salt to get seawater that is 9% salt.<BR>\n" );
document.write( "you were asked to evaporate pure water to get seawater that is 9% salt.<BR>\n" );
document.write( "that's a different equation.\r<BR>\n" );
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document.write( "that equation is:<BR>\n" );
document.write( "60.45 - x = .91 * (65 - x)<BR>\n" );
document.write( "you are evaporating x kilograms of pure water from a mixture that is 93% pure water to get a mixture that is 91% pure water, making it 9% salt.<BR>\n" );
document.write( "solve this equation and you will get x = 14.4444444.....<BR>\n" );
document.write( "60.45 - x = 46.0055555... kilograms of pure water that has not been evaporated and is therefore left in the mixture.<BR>\n" );
document.write( "65 - x = 50.555555..... kilograms of seawater that is left after the pure water has been evaporated.<BR>\n" );
document.write( "46 .0055555..... / 50.55555.... = .91 = 91% pure water.<BR>\n" );
document.write( "that makes the mixture 9% salt.\r<BR>\n" );
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document.write( "so your solutions become:<BR>\n" );
document.write( "add 26 kilograms of pure water to 65 kilograms of seawater that is 7% salt to get 91 kilograms of seawater that is 5% salt.<BR>\n" );
document.write( "evaporate 14.44444.... kilograms of pure water from seawater that is 7% salt to get 50.55555..... kilograms of seawater that is 9% salt.\r<BR>\n" );
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document.write( "in both cases, the amount of salt was not changed. the only changes was in the amount of pure water in the mixture.\r<BR>\n" );
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document.write( " </SPAN>\n" );
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