document.write( "Question 1006067: The ratio of boys to girls in a class is 3:4.I f there are 42 pupils in class, how many are girls? \n" ); document.write( "

Algebra.Com's Answer #622197 by ikleyn(52788) $\"\"$ $\"About$

You can put this solution on YOUR website!
.
\n" ); document.write( "

\r\n" );
document.write( "Let x = be the number of boys in the class, and y be the number of girls.\r\n" );
document.write( "\r\n" );
document.write( "Then you have two equations:\r\n" );
document.write( "\r\n" );
document.write( " = ,\r\n" );
document.write( "\r\n" );
document.write( "x + y = 42.\r\n" );
document.write( "\r\n" );
document.write( "Express x via y from the first equation: x = , and substitute it into the second equation. \r\n" );
document.write( "You will get a single equation for the unknown y:\r\n" );
document.write( "\r\n" );
document.write( " + y = 42.\r\n" );
document.write( "\r\n" );
document.write( "Multiply both sides by 4 and simplify.\r\n" );
document.write( "\r\n" );
document.write( "3y + 4y = 42*4 = 168,\r\n" );
document.write( "\r\n" );
document.write( "7y = 168, \r\n" );
document.write( "\r\n" );
document.write( "y =  = 24.\r\n" );
document.write( "\r\n" );
document.write( "Now x =  =  = 18.\r\n" );
document.write( "\r\n" );
document.write( "Answer. There are 18 boys and 24 girls in the class.\r\n" );
document.write( "

\n" ); document.write( " \n" ); document.write( "

\n" );