The washington family and the Reed family each uaed their sprinklers last summer, the water output rate for the washington family's sprinklers was 
15L per hour. the water output rate for the reeds family's sprinkler was 
20L per hour. The families used their sprinklers for a combined total of 
50 hours, resulting in a total water output of 
925 L.
How long was each sprinkler used?