Let the amount of work be L.
Therefore, the rate of work of the first team:
[tex]\frac{L}{14}[/tex]Similarly, the work rate of the second team is:
[tex]\frac{L}{18}[/tex]Therefore, the combined rate of both crews is given by:
[tex]\frac{L}{14}+\frac{L}{18}=\frac{8L}{63}[/tex]The time is given by:
[tex]\text{ time }=\frac{\text{ amount of work}}{\text{ rate}}[/tex]Therefore,
[tex]\text{ time }=L\div\frac{8L}{63}=L\times\frac{63}{8L}=\frac{63}{8}=7hours\text{ }53\text{ min}[/tex]Hence, the required time is 7 hours 53 minutes
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