Question 1041146: Ralph can lay down a floor tile in 5 seconds. Bob can lay down a floor tile in 4 seconds. If both boys work together, how many seconds would it take them to install 450 floor tiles?
Found 3 solutions by stanbon, MathTherapy, ikleyn:
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Ralph can lay down a floor tile in 5 seconds. Bob can lay down a floor tile in 4 seconds. If both boys work together, how many seconds would it take them to install 450 floor tiles?
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Ralph rate:: 1/5 tile/sec
Bob rate:: 1/4 tile/sec
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Together rate = (1/5) + (1/4) = 9/20 tile/sec
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Ans:: 450(9/20) = 22.5*9 = 201.6 seconds
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Cheers,
Stan H.
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Answer by MathTherapy(10555)  (Show Source):
You can put this solution on YOUR website!
Ralph can lay down a floor tile in 5 seconds. Bob can lay down a floor tile in 4 seconds. If both boys work together, how many seconds would it take them to install 450 floor tiles?
Ralph takes 2,250 seconds, alone, while Bob takes 1,800 seconds, alone
Time both take, working together: 
Answer by ikleyn(52817)  (Show Source):
You can put this solution on YOUR website! .
Ralph can lay down a floor tile in 5 seconds. Bob can lay down a floor tile in 4 seconds.
If both boys work together, how many seconds would it take them to install 450 floor tiles?
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Every 20 seconds Ralph lays 4 tiles and Bob lays 5 tiles.
So, every 20 seconds both boys lay 4 + 5 = 9 tiles working together.
 = 50.
Hence, the boys need 50*20 = 1000 seconds to lay all 450 tiles working together.
Answer. 1000 seconds.
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