Question

The Ross family and the Russell family each used their sprinklers last summer. The water output rate for the Ross family's sprinkler was 35L per hour. The water output rate for the Russell family's sprinkler was 30L per hour. The families used their sprinklers for a combined total of 55 hours, resulting in a total water output of 1725L. How long was each sprinkler used?

Answer 1

Ross = 15 hours

Russel = 40 hours

Explanation:

Let Ross have used their sprinklers for x hours

Let Russell have used their sprinklers for y hours

Together they used 55 hours

x+y = 55 hours

The output of Ross is 35 liters per hour and Russell is 30 liters per hour for a total of 1725

35x + 30y = 1725

Multiply the first equation by -30

-30(x+y=55)

-30x -30y = -1650

Add this to the second equation to eliminate y

-30x -30y = -1650

35x + 30y = 1725

-----------------------------

5x =75

Divide each side by 5

x = 15

Now find y

x+y = 55

y = 55-15

y = 40