Question

The Washington family and the Hall family each used their sprinklers last summer. The water output rate for the Washington family's sprinkler was 15L per hour. The water output rate for the Hall family's sprinkler was 35 L per hour. The families used their sprinklers for a combined total of 70 hours, resulting in a total water output of 1650L . How long was each sprinkler used?

Answer 1

• Washington: 40 hours
• Hall: 30 hours

Explanation:

If we let x and y represent usage time by the Washington and Hall families, respectively, the given relations can be written in equation form as ...

x + y = 70 . . . . . . combined total of 70 hours

15x +35y = 1650 . . . . total volume used

Substituting for x, we have ...

15(70 -y) +35y = 1650

20y +1050 = 1650 . . . . . simplify

20y = 600 . . . . . . . . . . subtract 1050

y = 30 . . . . . . . . . . . . divide by 20

70 -y = x = 70 -30 = 40 . . . . Washington family's usage

The Washington family sprinkler was used 40 hours; the Hall family sprinkler was used 30 hours.