SOLUTION: David can fill a pool in 10 hours. Working with Barney, they can fill the pool in 2 hours. How long does it take Barney to fill the pool if he works alone?
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-> SOLUTION: David can fill a pool in 10 hours. Working with Barney, they can fill the pool in 2 hours. How long does it take Barney to fill the pool if he works alone?
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Question 1145184: David can fill a pool in 10 hours. Working with Barney, they can fill the pool in 2 hours. How long does it take Barney to fill the pool if he works alone? Found 2 solutions by ikleyn, greenestamps:Answer by ikleyn(52832) (Show Source):
Working together, they make of the job per hour.
Working alone, David makes of the job per hour.
Hence, Barney makes - = = = of the work per hour.
It means that Barney will complete the job in hours = hours = 2 hours and 30 minutes.
Working together, it takes them 2 hours to fill the pool.
Since it takes David 10 hours to fill the pool, in 2 hours he fills 2/10 or 1/5 of the pool.
That means Barney fills 4/5 of the pool in 2 hours; since 4/5 is 4 times as much as 1/5, Barney works 4 times as fast as David.
Since Barney works 4 times as fast as David, it will take him 1/4 as long as David to fill the pool by himself.
1/4 of 10 hours is 2.5 hours.
