document.write( "Question 838759: I don't know where to start, please help!
\n" ); document.write( "Albert invests money in three accounts that pay 4%, 10%, and 15%. He has two times as much money invested at 10% than he does at 15%. If the total amount he has invested is $4,950 and his interest for the year comes to $520, how much money does he have in each account?
\n" ); document.write( "I know how to do it when there are only two varialbes, but no clue how to do it where there are three. \n" ); document.write( "

Algebra.Com's Answer #505334 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
There are 3 unknowns, and you can get
\n" ); document.write( "3 equations from given data
\n" ); document.write( "---------------------------
\n" ); document.write( "Let $\"+a+\"$ = amount invested @ 4%
\n" ); document.write( "Let $\"+b+\"$ = amount invested @ 10%
\n" ); document.write( "Let $\"+c+\"$ = amount invested @ 15%
\n" ); document.write( "----------------------------------
\n" ); document.write( "(1) $\"+a+%2B+b+%2B+c+=+4950+\"$
\n" ); document.write( "(2) $\"+.04a+%2B+.1b+%2B+.15c+=+520+\"$
\n" ); document.write( "(3) $\"+b+=+2c+\"$
\n" ); document.write( "-------------------------------
\n" ); document.write( "(2) $\"+4a+%2B+10b+%2B+15c+=+52000+\"$
\n" ); document.write( "and
\n" ); document.write( "Multiply both sides of (1) by $\"+4+\"$
\n" ); document.write( "and subtract (1) from (2)
\n" ); document.write( "(2) $\"+4a+%2B+10b+%2B+15c+=+52000+\"$
\n" ); document.write( "(1) $\"+-4a+-+4b+-+4c+=+-19800+\"$
\n" ); document.write( " $\"+6b+%2B+11c+=+32200+\"$
\n" ); document.write( "Substitute (3) into this result
\n" ); document.write( " $\"+6%2A%282c%29+%2B+11c+=+32200+\"$
\n" ); document.write( " $\"+23c+=+32200+\"$
\n" ); document.write( " $\"+c+=+1400+\"$
\n" ); document.write( "and, since
\n" ); document.write( "(3) $\"+b+=+2c+\"$
\n" ); document.write( "(3) $\"+b+=+2800+\"$
\n" ); document.write( "and
\n" ); document.write( "(1) $\"+a+%2B+b+%2B+c+=+4950+\"$
\n" ); document.write( "(1) $\"+a+%2B+2800+%2B+1400+=+4950+\"$
\n" ); document.write( "(1) $\"+a+%2B+4200+=+4950+\"$
\n" ); document.write( "(1) $\"+a+=+750+\"$
\n" ); document.write( "-----------------
\n" ); document.write( "$750 is invested @ 4%
\n" ); document.write( "$2800 is invested @ 10%
\n" ); document.write( "$1400 is invested @ 15%
\n" ); document.write( "----------------------
\n" ); document.write( "check:
\n" ); document.write( "(2) $\"+.04a+%2B+.1b+%2B+.15c+=+520+\"$
\n" ); document.write( "(2) $\"+.04%2A750+%2B+.1%2A2800+%2B+.15%2A1400+=+520+\"$
\n" ); document.write( "(2) $\"+30+%2B+280+%2B+210+=+520+\"$
\n" ); document.write( "(2) $\"+520+=+520+\"$
\n" ); document.write( "OK \n" ); document.write( "

\n" );