document.write( "Question 1025945: BJ can overhaul a boat's diesel inboard engine in 20 hours. His apprentice takes 6 hours to do the same job. how long would it take them working together assuming no gain or loss in efficiency \n" ); document.write( "

Algebra.Com's Answer #641206 by josmiceli(19441) $\"\"$ $\"About$

You can put this solution on YOUR website!
First of all, you have to imagine 2 people working
\n" ); document.write( "on an engine without getting in eachother's way.
\n" ); document.write( "It's not like painting a fence.
\n" ); document.write( "But as long as you can assume that, add their
\n" ); document.write( "rates of working to get their rate working together.
\n" ); document.write( "BJ's rate:
\n" ); document.write( "[ 1 engine overhauled ] / [ 20 hrs ]
\n" ); document.write( "Apprentice's rate:
\n" ); document.write( "[ 1 engine overhauled ] / [ 6 hrs ]
\n" ); document.write( "Let $\"+t+\"$ = their time in hrs working together
\n" ); document.write( "to overhaul engine
\n" ); document.write( "Rate working together:
\n" ); document.write( "[ 1 engine overhauled ] / [ t hrs ]
\n" ); document.write( "------------------------------
\n" ); document.write( " $\"+1%2F20+%2B+1%2F6+=+1%2Ft+\"$
\n" ); document.write( "Multiply both sides by $\"+60t+\"$
\n" ); document.write( " $\"+3t+%2B+10t+=+60+\"$
\n" ); document.write( " $\"+13t+=+60+\"$
\n" ); document.write( " $\"+t+=+4+%2B+8%2F60+\"$
\n" ); document.write( "Working together, it takes them 4 hrs and 8 min
\n" ); document.write( "check:
\n" ); document.write( " $\"+1%2F20+%2B+1%2F6+=+1%2Ft+\"$
\n" ); document.write( " $\"+1%2F20+%2B+1%2F6+=+1%2F%2860%2F13%29+\"$
\n" ); document.write( " $\"+1%2F20+%2B+1%2F6+=+13%2F60+\"$
\n" ); document.write( " $\"+3%2F60+%2B+10%2F60+=+13%2F60+\"$
\n" ); document.write( " $\"+13%2F60+=+13%2F60+\"$
\n" ); document.write( "OK \n" ); document.write( "

\n" );