document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=78918>Question 78918</A>: <I><SPAN STYLE=\"word-break: break-all;\"> A certain sum of money is invested at 10%. Twice that amount is invested at 8%. The total amount of interest from both investment is $91. How much is invested at 8%? </SPAN>\n" );
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document.write( "OK i will try to answer this one since I like answering and since my dad once tried to teach me about compound interest.  Compound interest is not involved in this problem and it is hard to get a credit card company to give you their formula I think.\r<BR>\n" );
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document.write( "The problem says, as I see it, <BR>\n" );
document.write( "  X is invested at 10%<BR>\n" );
document.write( " 2X is invested at 8%<BR>\n" );
document.write( "The total interest is $91<BR>\n" );
document.write( "What is invested at 8% ?\r<BR>\n" );
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document.write( "where X is \"a certain sum that is invested\".\r<BR>\n" );
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document.write( "What you will do is solve for X using the given information, and then as the final anwer give 2x since that is the quantity requested in the problem statement.\r<BR>\n" );
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document.write( "Generally investment rates are computed per year, so I am assuming the investment period they are talking about is 1 year, and I don't have to worry about compounding it where you'd compute (1.10)^N (N is the number of years) or (1.08)^N either.  They are just talking about some situation where you put your money in and later you get back 10% or 8% more and then the deal is done.\r<BR>\n" );
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document.write( "So you have X * (1.10) + 2X * (1.08) = 91 as your equation to solve\r<BR>\n" );
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document.write( "It helps to know when they say \"percent\" they are talking about hundredths.  There are ten fingers on a person's hands, ten pennies in a dime, and a hundred pennies in a dollar, and a hundred centimetres in a metre, so being human and living on planet Earth means you know \"percent\" means a hundredth.  Ten percent is written as 0.10 or 10/100 and when you earn ten percent that is added to 1 which is 1.00 so you can see 1.00 + 0.10 = 1.10 which is the original amount plus ten per cent interest.\r<BR>\n" );
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document.write( "Now you have 3.26 X = 91 \r<BR>\n" );
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document.write( "I am using my calculator to divide 91/3.26 but you could also use long division\r<BR>\n" );
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document.write( "X = 91/ 3.26 = 27.92  and I have rounded up from 27.913 because I want to have at least $91 when I am done, not less.  Your teacher may want you to round to X=27.91 instead.\r<BR>\n" );
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document.write( "The answer to the problem is closer to 55.83\r<BR>\n" );
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document.write( "Check this: <BR>\n" );
document.write( "55.83 plus 8 percent = 60.30  (55.83 * 1.08)<BR>\n" );
document.write( "27.91 plus 10 percent = 30.70  (27.91 * 1.10)\r<BR>\n" );
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document.write( "Total is 91.00\r<BR>\n" );
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document.write( " </SPAN>\n" );
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