Answer:
The Martins used their sprinkler for 35 hours, while the Kellys used their sprinkler for 25 hours.
Step-by-step explanation:
As the Martins and the Kellys used their sprinklers for 60 hours combined last summer, and the water output rate of the Martins' sprinkler is 30 liters per hour, while the Kelly's is 35 liters per hour To determine how many hours each family used their sprinklers, knowing that in total 1925 liters of water were used, the following logical reasoning must be carried out:
There is a 5 liter difference between the Kelly sprinkler and the Martin sprinkler. If both used 30 liters of water per hour, for 60 hours 1800 liters (30 x 60) would have been used. Therefore, there is an excess of 125 liters that corresponds to an excess of consumption, attributable to the Kelly sprinkler, which consumes 5 liters more of water per hour than the Martin's. Thus, since 125/5 equals 25, in total the Kellys used their sprinkler for 25 hours, while the Martins did it for 35 hours.
This reasoning is proved with the following calculation:
25 x 35 = 875
35 x 30 = 1,050
875 + 1,050 = 1,925
