document.write( "Question 754815: Mark can clean his fathers office in 30 min. His younger sister Lynn can clean the office in 40 min. How long will it take the two of them together to clean the office? \n" ); document.write( "

Algebra.Com's Answer #459315 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
Add their rates of cleaning
\n" ); document.write( "Mark's rate:
\n" ); document.write( "( 1 office cleaned ) / ( 30 min )
\n" ); document.write( "Lynn's rate:
\n" ); document.write( "( 1 office cleaned ) / ( 40 min )
\n" ); document.write( "Let $\"+t+\"$ = the time in minutes for them
\n" ); document.write( "to clean the office working together
\n" ); document.write( "------------------------------
\n" ); document.write( " $\"+1%2F30+%2B+1%2F40+=+1%2Ft+\"$
\n" ); document.write( "Multiply both sides by $\"+120t+\"$
\n" ); document.write( " $\"+4t+%2B+3t+=+120+\"$
\n" ); document.write( " $\"+7t+=+120+\"$
\n" ); document.write( " $\"+t+=+17.143+\"$ min
\n" ); document.write( "check answer:
\n" ); document.write( " $\"+1%2F30+%2B+1%2F40+=+1%2Ft+\"$
\n" ); document.write( " $\"+.0333+%2B+.025+=+1%2F17.143+\"$
\n" ); document.write( " $\"+.05833+=+.05833+\"$
\n" ); document.write( "OK
\n" ); document.write( " \n" ); document.write( "

\n" );