Question 546943
It takes 6 workers 3 days to build one house.  So the rate of building is:
1 house/(6 workers*3 days) = 1 house per 18 worker-days
To build in one day we need 
1 house/18 worker-days * 1 day = 1 house per 18 workers
Therefore it takes 18 workers to build 1 house in 1 day