document.write( "Question 1149106: A man saved 3000 in a bank p, whose interest rate was X% per annum and 2000 in another bank Q whose interest rate was Y% per annum. His total interest in one year was 640. If he had saved 2000 in P and 3000 in Q for the same period, he would have gained 20 as additional interest. Find
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document.write( "(I) the value of x and Y.
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document.write( "(II) the investment return if the man saves 5000 in bank Q for 2years. \n" );
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Algebra.Com's Answer #770437 by Theo(13342)![]() ![]() You can put this solution on YOUR website! let x = the interest rate for investment P. \n" ); document.write( "let y = the interest rate for investment Q.\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "you get:\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "3000x + 2000y = 640 \n" ); document.write( "2000x + 3000y = 660\r \n" ); document.write( " \n" ); document.write( "\n" ); document.write( "multiply both sides of the first equation by 2 and multiply both sides of the second equation by 3 to get: \n" ); document.write( "6000x + 4000y = 1280 \n" ); document.write( "6000x + 9000y = 1980 \n" ); document.write( "subtract the first equation from the second to get: \n" ); document.write( "5000y = 700 \n" ); document.write( "solve for y to get: \n" ); document.write( "y = .14 \n" ); document.write( "replace y with .14 in the first original equation to get: \n" ); document.write( "3000x + 2000y = 640 becomes 3000x + 2000*.14 = 640 which becomes 3000x + 280 = 640. \n" ); document.write( "subtract 280 from both sides of this equation to get: \n" ); document.write( "3000x = 640 - 280 which becomes 3000x = 360. \n" ); document.write( "solve for x to get x = 360/3000 = .12 \n" ); document.write( "you have x = .12 and y = .14 \n" ); document.write( "go back to your two original equations and replace x with .12 and y with .14 to get: \n" ); document.write( "3000x + 2000y = 640 becomes 3000*.12 + 2000*.14 = 640 which becomes 360 + 280 = 640 which becomes 640 = 640 which is true. \n" ); document.write( "2000x + 3000y = 660 becomes 2000*.12 + 3000*.14 = 660 which becomes 240 + 420 = 660 which becomes 660 = 660 which is true. \n" ); document.write( "both original equations are true when x = .12 and y = .14. \n" ); document.write( "x% = x * 100 = 12% \n" ); document.write( "y% = y * 100 = 14%. \n" ); document.write( "since they asked for the value of x and y, and not for the value of x% and y%, your solution is x = .12 and y = .14. \n" ); document.write( "if the man has put all 5000 in bank Q, then he would have earned interest of 5000 * .14 = 700.\r \n" ); document.write( "\n" ); document.write( " \n" ); document.write( " |