Question 1041146
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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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<pre>
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.

{{{450/9}}} = 50.

Hence, the boys need 50*20 = 1000 seconds to lay all 450 tiles working together.

<U>Answer</U>.  1000 seconds.
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