document.write( "Question 751337: Jeremy and his dad can wash his car together in 40 minutes, Jeremy can wash it by himself in 70 minutes. How long would it take his dad to wash it by himself? \n" ); document.write( "

Algebra.Com's Answer #457165 by josmiceli(19441) $\"\"$ $\"About$

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Add their rates of washing to get their rate
\n" ); document.write( "working together
\n" ); document.write( "Let $\"+t+\"$ = minutes for Dad to wash car
\n" ); document.write( "( 1 car / 70 min ) + ( 1 car / t min ) = ( 1 car / 40 min )
\n" ); document.write( " $\"+1+%2F70+%2B+1%2Ft+=+1%2F40+\"$
\n" ); document.write( "Multiply both sides by $\"+280t+\"$
\n" ); document.write( " $\"+4t+%2B+280+=+7t+\"$
\n" ); document.write( " $\"+3t+=+280+\"$
\n" ); document.write( " $\"+t+=+93.+333+\"$
\n" ); document.write( " $\"+93.333+-+60+=+33.333+\"$
\n" ); document.write( "Dad will take 1 hour 33 min and 20 sec
\n" ); document.write( "check:
\n" ); document.write( " $\"+1+%2F70+%2B+1%2Ft+=+1%2F40+\"$
\n" ); document.write( " $\"+1+%2F70+%2B+1%2F93.333+=+1%2F40+\"$
\n" ); document.write( " $\"+.0142857+%2B+.0107143+=+.025+\"$
\n" ); document.write( " $\"+.025+=+.025+\"$
\n" ); document.write( "OK
\n" ); document.write( " \n" ); document.write( "

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