document.write( "Question 204667: A man can paint a room by himself in 8 hours and it takes his son 12 hours to do the same job. The man works by himself for three hours, then his son joins him and the two together complete the job. How long does the son work? \n" ); document.write( "

Algebra.Com's Answer #154466 by Earlsdon(6294) $\"\"$ $\"About$

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If the man can paint the room in 8 hours, then he can paint $\"1%2F8\"$ of the room in 1 hour.
\n" ); document.write( "If his son can paint the room in 12 hours, then he can paint $\"1%2F12\"$ of the room in 1 hour.
\n" ); document.write( "Now if the man works by himself for 3 hours, then he can paint:
\n" ); document.write( " $\"3%2A%281%2F8%29+=+3%2F8\"$ of the room which leaves $\"5%2F8\"$ of the room to paint.
\n" ); document.write( "Now the man and his son, working together can paint $\"1%2F8+%2B+1%2F12+=+5%2F24\"$ of the room in 1 hour.
\n" ); document.write( "So the question is, how long would it take the father & son together to finish the $\"5%2F8\"$ of the room?
\n" ); document.write( "To find this, we'll divide the $\"5%2F8\"$ by $\"5%2F24\"$ .
\n" ); document.write( " $\"%285%2F8%29%2F%285%2F24%29+=+%285%2F8%29%2A%2824%2F5%29\"$ = $\"3\"$ .
\n" ); document.write( "The son works for 3 hours. \n" ); document.write( "

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