document.write( "Question 641755: Two certificates of deposit pay interest rates that differ by 2%. For the first CD, the money is invested for a year and earns $200 interest. For the second CD the same amount of money invested earns $255 in a year. What is the interest rate of the first CD account (rounded to the nearest tenth)? \n" ); document.write( "

Algebra.Com's Answer #403781 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Let $\"+c+\"$ = the speed of the current
\n" ); document.write( " $\"+3+%2B+c+\"$ = dog's speed going downstream
\n" ); document.write( " $\"+3+-+c+\"$ = dog's speed going upstream
\n" ); document.write( "Let $\"+t+\"$ = dog's time to travel downstream
\n" ); document.write( " $\"+12+-+t+\"$ = dog's time to travel upstream
\n" ); document.write( "---------------------------------
\n" ); document.write( "Equation going downstream:
\n" ); document.write( "(1) $\"+10+=+%28+3+%2B+c+%29%2At+\"$
\n" ); document.write( "Equation going upstream:
\n" ); document.write( "(2) $\"+10+=+%28+3+-+c+%29%2A%28+12+-+t+%29+\"$
\n" ); document.write( "------------------------
\n" ); document.write( "(1) $\"+t+=+10+%2F+%28+3+%2B+c+%29+\"$
\n" ); document.write( "and
\n" ); document.write( "(2) $\"+10+=+36+-+12c+-+3t+%2B+c%2At+\"$
\n" ); document.write( "Substitute (1) into (2)
\n" ); document.write( "(2) $\"+10+=+36+-+12c+-+3%2A10+%2F+%28+3+%2B+c+%29+%2B+10c+%2F+%28+3+%2B+c+%29+\"$
\n" ); document.write( "(2) $\"+-26+=++-+12c+-+30+%2F+%28+3+%2B+c+%29+%2B+10c+%2F+%28+3+%2B+c+%29+\"$
\n" ); document.write( "Multiply both sides by $\"+3+%2B+c+\"$
\n" ); document.write( "(2) $\"+-26%2A%28+3+%2B+c+%29+=+-12c%2A%28+3+%2B+c+%29+-+30+%2B+10c+\"$
\n" ); document.write( "Multiply both sides by $\"+-1+\"$
\n" ); document.write( "(2) $\"+78+%2B+26c+=+36c+%2B+12c%5E2+%2B+30+-+10c+\"$
\n" ); document.write( "(2) $\"+12c%5E2+=+48+\"$
\n" ); document.write( "(2) $\"+c%5E2+=+4+\"$
\n" ); document.write( "(2) $\"+c+=+2+\"$
\n" ); document.write( "The speed of the current is 2 mi/hr
\n" ); document.write( "check:
\n" ); document.write( "(1) $\"+10+=+%28+3+%2B+2+%29%2At+\"$
\n" ); document.write( "(1) $\"+t+=+10%2F5+\"$
\n" ); document.write( "(1) $\"+t+=+2+\"$ hrs
\n" ); document.write( "and
\n" ); document.write( "(2) $\"+10+=+%28+3+-+2+%29%2A%28+12+-+t+%29+\"$
\n" ); document.write( "(2) $\"+10+=+12+-+t+\"$
\n" ); document.write( "(2) $\"+t+=+2+\"$ hrs
\n" ); document.write( "OK- I get the same answer \n" ); document.write( "

\n" );