document.write( "Question 816750: Phyllis invested $12,000, a portion earning a simple interest rate of 4.5% per year and the rest earning a rate of 4% per year. After 1 year the total interest earned on these investments was $525. How much did she invest at each rate?\r
\n" ); document.write( "\n" ); document.write( "I am constantly getting this answer wrong. The book is saying 30, but when I follow the equation
\n" ); document.write( "0.04x +0.045(12000-x)=525\r
\n" ); document.write( "\n" ); document.write( "my answer is way off. Maybe I'm working out the wrong equation. \n" ); document.write( "
Algebra.Com's Answer #491699 by rothauserc(4718)\"\" \"About 
You can put this solution on YOUR website!
simple interest is calculated with this formula I = prt, where p is principal, r is rate and t is time,
\n" ); document.write( "in this case t is 1 year
\n" ); document.write( "0.04x +0.045(12000-x)=525 is setup correctly
\n" ); document.write( "0.04x +540 -0.045x = 525
\n" ); document.write( "-0.005x = -15
\n" ); document.write( "x = 3000
\n" ); document.write( "The problem asks us how much money was invested at 4% and 4.5% given that Phyllis had $12,000 to invest. Our calculation shows the following
\n" ); document.write( "$3,000 invested at 4%
\n" ); document.write( "$9,000 invested at 4.5%
\n" ); document.write( "We are also told that Phyllis earned $525 in interest from both investments
\n" ); document.write( "now check the answers
\n" ); document.write( "0.04*3000 + 0.045*9000 = $120 + $405 = $525
\n" ); document.write( "our answers check
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