document.write( "Question 142764: I know how to solve a linear equation with three variables by using two of the three equations to eliminate one variable and then use a different pair of equations to eliminate the same variable and then you can solve those equations. I am doing some word problems and writing the first two equations with three unknown variables is easy but I cannot seem to write the third.\r
\n" );
document.write( "\n" );
document.write( "Mike has 19 coins (nickels, dimes and quarters) in his piggy bank with a total value of $2.35. There are 2 more dimes than nickels. How many of each type does Mike have?\r
\n" );
document.write( "\n" );
document.write( "N+D+Q=19
\n" );
document.write( "5N+10D+25Q=235
\n" );
document.write( "?\r
\n" );
document.write( "
\n" );
document.write( "\n" );
document.write( "With the first two I can multiply the first by –5 to eliminate N. I need another equation. Help?\r
\n" );
document.write( "\n" );
document.write( "----------------
\n" );
document.write( "Fred, Tiger and Nancy play a round of golf together. Their combined score is 223. Fred’s score was 3 more than Nancy’s and Tiger’s score was 7 more than Fred’s. What was each person’s score. \r
\n" );
document.write( "\n" );
document.write( "You would think something simple like
\n" );
document.write( "F=N+3
\n" );
document.write( "T=F+7
\n" );
document.write( "223=T+F+N\r
\n" );
document.write( "\n" );
document.write( "But I need three equations with three unknown variables. \n" );
document.write( "
Algebra.Com's Answer #103878 by checkley77(12844)![]() ![]() ![]() You can put this solution on YOUR website! N+D+Q=19 \n" ); document.write( "5N+10D+25Q=235 \n" ); document.write( "D=N+2 IS THE THIRD EQUATION. \n" ); document.write( "N+(N+2)+Q=19 \n" ); document.write( "2N+2+Q=19 \n" ); document.write( "2N+Q=19-2 \n" ); document.write( "2N+Q=17 MULTIPLY THIS EQUATION BY -25 & ADD IT TO THE [15N+25Q=215] EQUATION \n" ); document.write( "5N+10(N+2)+25Q=235 \n" ); document.write( "5N+10N+20+25Q=235 \n" ); document.write( "15N+25Q=235-20 \n" ); document.write( "15N+25Q=215 \n" ); document.write( "-50N-25Q=-425 \n" ); document.write( "-------------------------- \n" ); document.write( "-35N=-210 \n" ); document.write( "N=-210/-35 \n" ); document.write( "N=6 ANSWER FOR THE NUMBER OF NICKELS. \n" ); document.write( "D=6+2 \n" ); document.write( "D=8 ANSWER FOR THE NUMBER OF DIMES. \n" ); document.write( "2*6+Q=17 \n" ); document.write( "12+Q=17 \n" ); document.write( "Q=17-12 \n" ); document.write( "Q=5 NUMBER OF QUARTERS. \n" ); document.write( "PROOF: \n" ); document.write( "6+8+5=19 \n" ); document.write( "19=19 \n" ); document.write( "AND: \n" ); document.write( "5*6+10*8+25*5=235 \n" ); document.write( "30+80+125=235 \n" ); document.write( "235=235 \n" ); document.write( "------------------------------------------------------ \n" ); document.write( "YOU HAVE THE THREE REQUIRED EQUATION HOWEVER YOU DO NOT NEED ALL THREE VARIABLES IN EACH EQUATION. iN FACT IT IS EASIER TO SOLVE IF THERE ARE ONLY TWO VARIABLES. \n" ); document.write( "F=N+3 \n" ); document.write( "T=F+7 OR T=(N+3)+7 OR T=N+10 \n" ); document.write( "223=T+F+N OR 223=(N+10)+(N+3)+N \n" ); document.write( "223=N+10+N+3+N \n" ); document.write( "223=3N+13 \n" ); document.write( "3N=223-13 \n" ); document.write( "3N=210 \n" ); document.write( "N=210/3 \n" ); document.write( "N=70 FOR NANCY'S SCORE. \n" ); document.write( "F=70+3=73 FOR FRED'S SCORE. \n" ); document.write( "T=73+7=80 FOR TIGER'S SCORE. \n" ); document.write( "PROOF: \n" ); document.write( "223=70+73+80 \n" ); document.write( "223=223 \n" ); document.write( " \n" ); document.write( " |