document.write( "Question 1058851: a person invested Rs.1000 at 5% interest rate and allow to grow till it increased by 80%. in how many years did this happen? \n" ); document.write( "
Algebra.Com's Answer #673947 by Theo(13342)\"\" \"About 
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the increase is 80% of 1000 which is equal to 800.
\n" ); document.write( "the future value is 1000 + 800 = 1800.
\n" ); document.write( "the formula is f = p * (1+r)^n
\n" ); document.write( "f is the future value.
\n" ); document.write( "p is the present value.
\n" ); document.write( "r is the interest rate per time period.
\n" ); document.write( "n is the number of time periods.
\n" ); document.write( "the formula becomes:
\n" ); document.write( "1800 = 1000 * (1.05)^n
\n" ); document.write( "divide both sides by 1000 to get:
\n" ); document.write( "1.8 = 1.05^n
\n" ); document.write( "take the log of both sides to get:
\n" ); document.write( "log(1.8) = log(1.05^n)
\n" ); document.write( "this becomes:
\n" ); document.write( "log(1.8) = n * log(1.05)
\n" ); document.write( "divide both sides by log(1.05) to get:
\n" ); document.write( "log(1.8)/log(1.05) = n
\n" ); document.write( "solve for n to get n = log(1.8)/log(1.05) = 12.04723687
\n" ); document.write( "the 1000 will grow to 1800 in 12.04723687 years.
\n" ); document.write( "f = 1000 * (1.05)^12.04723687 which is equal to 1800.
\n" ); document.write( "solution is confirmed to be correct.\r
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