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 March 14th, 2019, 01:30 PM #1 Senior Member   Joined: Dec 2015 From: somewhere Posts: 600 Thanks: 88 Total time problem First worker capacity alone to do the work : 12 hours Second worker capacity alone to do the work : 6 hours They start working together for 3 hours and then the second worker continues to work alone . How much time the second worker did work ? Last edited by idontknow; March 14th, 2019 at 02:05 PM.
 March 14th, 2019, 02:16 PM #2 Global Moderator   Joined: Dec 2006 Posts: 20,931 Thanks: 2207 In total, 4 1/2 hours. Thanks from idontknow
March 14th, 2019, 02:25 PM   #3
Math Team

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Quote:
 Originally Posted by idontknow First worker capacity alone to do the work : 12 hours Second worker capacity alone to do the work : 6 hours They start working together for 3 hours and then the second worker continues to work alone . How much time the second worker did work ?
$t$ is number of hours worker 2 worked alone

$3\left(\dfrac{1}{12} + \dfrac{1}{6} \right) + t \cdot \dfrac{1}{6} = 1$

 March 14th, 2019, 03:03 PM #4 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,597 Thanks: 1038 To "see" it clearly, make up something simple, like: make "the work" = travelling 120 miles; 1st driver's speed = 10 mph, 2nd driver's speed = 20 mph: @(20+10)mph.......90m........>3hr@20mph....30m.... ..>1.5hr Clear? Thanks from idontknow

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