document.write( "Question 1039408: A sum of money amounts to Rs 5200 in 5 years and Rs 5680 in 7 years at simple interest .What was the rate of simple interest charged per annum ? \n" ); document.write( "

Algebra.Com's Answer #654252 by Aldorozos(172) $\"\"$ $\"About$

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f = p(1+r)^n where f is the future value, p is the present value, r is the interest rate and n is the number of periods\r
\n" ); document.write( "\n" ); document.write( "5200 = p (1+r)^5
\n" ); document.write( "5680 = p(1+r)^7\r
\n" ); document.write( "\n" ); document.write( "From 5200 = p (1+r)^5
\n" ); document.write( " we calculate p\r
\n" ); document.write( "\n" ); document.write( "p = 5200/(1+r)^5\r
\n" ); document.write( "\n" ); document.write( "Similarly we calculate p from
\n" ); document.write( "5680 = p(1+r)^7\r
\n" ); document.write( "\n" ); document.write( "and we get p = 5680/(1+r)^7\r
\n" ); document.write( "\n" ); document.write( "We set the two equations together since both are equal to p\r
\n" ); document.write( "\n" ); document.write( "5200/(1+r)^5 = 5680/(1+r)^7\r
\n" ); document.write( "\n" ); document.write( "5680/5200 = (1+r)^7 divided by (1+r)^5
\n" ); document.write( "(1+r)^2 = 1.0923
\n" ); document.write( "Square root of 1.0923 is 1.045\r
\n" ); document.write( "\n" ); document.write( "1+r = 1.045
\n" ); document.write( "therefore r - 1.045 - 1 = .045 = 4.5%\r
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