document.write( "Question 1138669: A $132,000 trust is to be invested in bonds paying 8%, CDs paying 6%, and mortgages paying 10%. The bond and CD investment together must equal the mortgage investment. To earn a $11,200 annual income from the investments, how much should the bank invest in bonds?
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Algebra.Com's Answer #756490 by MathTherapy(10552)\"\" \"About 
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A $132,000 trust is to be invested in bonds paying 8%, CDs paying 6%, and mortgages paying 10%. The bond and CD investment together must equal the mortgage investment. To earn a $11,200 annual income from the investments, how much should the bank invest in bonds?
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Let amount invested in bonds, CDs, and mortgages be B, C, and M, respectively
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document.write( "Then we get: B + C + M = 132,000 ------ eq (i)
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document.write( "Also, B + C = M ------- eq (ii)
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document.write( "And, .08B + .06C + .1M = 11,200_____2(.04B + .03C + .05M) = 2(5,600)_____.04B + .03C + .05M = 5,600 ------- eq (iii)\r
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document.write( "2M = 132,000 ------ Substituting M for B + C in eq (i)
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document.write( "\"matrix%281%2C5%2C+M%2C+%22=%22%2C+%22132%2C000%22%2F2%2C+%22=%22%2C+%22%2466%2C000%22%29\", and so, B + C = 66,000 ======> C = 66,000 - B
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document.write( ".04B + .03(66,000 - B) + .05(66,000) = 5,600 ------ Substituting 66,000 - B for C, and 66,000 for M in eq (iii)
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document.write( ".04B + 1,980 - .03B + 3,300 = 5,600
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document.write( ".04B - .03B = 5,600 - 5,280
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document.write( ".01B = 320
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document.write( "Amount invested in bonds, or  \n" );
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