document.write( "Question 1210268: A sum of money amounts to ₦5,280 in 4 years at a certain rate of simple interest. If the same amount is invested at a 2% higher interest rate, it amounts to ₦5,520 in the same time.
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Algebra.Com's Answer #851778 by ikleyn(52781) $\"\"$ $\"About$

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\n" ); document.write( "A sum of money amounts to ₦5,280 in 4 years at a certain rate of simple interest.
\n" ); document.write( "If the same amount is invested at a 2% higher interest rate, it amounts to ₦5,520 in the same time.
\n" ); document.write( "Find:
\n" ); document.write( "- The principal
\n" ); document.write( "- The original rate of interest
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document.write( "Let A be the amount (the same in both cases).\r\n" );
document.write( "Let r be the original interest (in the decimal form).\r\n" );
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document.write( "Then from the problem, we have these two equations\r\n" );
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document.write( "    5280 = A*(1+4r),           (1)\r\n" );
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document.write( "    5520 = A*(1+4(r+0.02)).    (2)\r\n" );
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document.write( "Divide equation (1) by equation (2).  You will get\r\n" );
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document.write( "     = ,\r\n" );
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document.write( "     = \r\n" );
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document.write( "    22*(1.08+4r) = 23*(1+4r)\r\n" );
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document.write( "    23.76 + 88r = 23 + 92r\r\n" );
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document.write( "    23.76 - 23 = 92r - 88r\r\n" );
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document.write( "        0.76   =     4r\r\n" );
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document.write( "           r   =      = 0.19.\r\n" );
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document.write( "Then from equation (1)\r\n" );
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document.write( "    A =  = 3000.\r\n" );
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document.write( "ANSWER.  The principal was N3000.  The annual interest was 0.19, or 19%.\r\n" );
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