document.write( "Question 935621: please help me solving it.i tried it again and again but still not getting it. some amount out of $7000 was lent at 6% p.a. and the remaining was lent at 4%p.a.
\n" ); document.write( "if the total simple interest in 5 years was $1600, find the amount lent 6% p.a
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Algebra.Com's Answer #568862 by Theo(13342)\"\" \"About 
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let x equal the amount invested at 6%.
\n" ); document.write( "let y equal the amount invested at 4%.\r
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\n" ); document.write( "\n" ); document.write( "total amount invested is 7000, so x + y = 7000\r
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\n" ); document.write( "\n" ); document.write( "simple interest formula is:\r
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\n" ); document.write( "\n" ); document.write( "i = n * r * p\r
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\n" ); document.write( "\n" ); document.write( "i = total interest
\n" ); document.write( "n = number of years
\n" ); document.write( "r = annual rate of interest
\n" ); document.write( "p = principal\r
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\n" ); document.write( "\n" ); document.write( "x is the principal that is invested at 6%.
\n" ); document.write( "y is the principal that is invested at 4%.\r
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\n" ); document.write( "\n" ); document.write( "total interest is 1600, so 5 * .06 * x + 5 * .04 * y = 1600\r
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\n" ); document.write( "\n" ); document.write( "you have 2 equations that need to be solved simultaneously.\r
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\n" ); document.write( "\n" ); document.write( "they are:\r
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\n" ); document.write( "\n" ); document.write( "x + y = 7000
\n" ); document.write( "5 * .06 * x + 5 * .04 * y = 1600\r
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\n" ); document.write( "\n" ); document.write( "simplify the second equation to get:\r
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\n" ); document.write( "\n" ); document.write( "5 * .06 * x + 5 * .04 * y = 1600 becomes:
\n" ); document.write( ".3 * x + .2 * y = 1600\r
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\n" ); document.write( "\n" ); document.write( "your 2 equations now are:\r
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\n" ); document.write( "\n" ); document.write( "x + y = 7000
\n" ); document.write( ".3 * x + .2 * y = 1600\r
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\n" ); document.write( "\n" ); document.write( "solve for y in the first equation to get y = 7000 - x.\r
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\n" ); document.write( "\n" ); document.write( "substitute 7000 - x for y in the second equation to get:\r
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\n" ); document.write( "\n" ); document.write( ".3 * x + .2 * (7000 - x) = 1600\r
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\n" ); document.write( "\n" ); document.write( "solve for x in this equation:\r
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\n" ); document.write( "\n" ); document.write( "start with:
\n" ); document.write( ".3 * x + .2 * (7000 - x) = 1600
\n" ); document.write( "distribute the multiplication to get:
\n" ); document.write( ".3 * x + .2 * 7000 - .2 * x = 1600
\n" ); document.write( "simplify to get:
\n" ); document.write( ".3 * x + 1400 - .2 * x = 1600
\n" ); document.write( "combine like terms to get:
\n" ); document.write( ".1 * x + 1400 = 1600
\n" ); document.write( "subtract 1400 from both sides of the equation to get:
\n" ); document.write( ".1 * x = 200
\n" ); document.write( "divide both sides of the equation by .1 to get:
\n" ); document.write( "x = 2000\r
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\n" ); document.write( "\n" ); document.write( "since x + y = 7000, and x = 2000, then y must be equal to 5000.\r
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\n" ); document.write( "\n" ); document.write( "x + y = 7000 becomes 2000 + 5000 = 7000 which becomes 7000 = 7000 which is good.\r
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\n" ); document.write( "\n" ); document.write( "5 * .06 * x + 5 * .04 * y = 1600 becomes .3 * 2000 + .2 * 5000 = 1600 which becomes 600 + 1000 = 1600 which becomes 1600 = 1600 which is also good.\r
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\n" ); document.write( "\n" ); document.write( "the solution looks good and your answer is that the amount lent at 6% per year is equal to 2000.\r
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